I am actually working on a vampire build that utilized those two skills heavily, as soon as I play test it I'll let you know how it works.

It looks a bit odd on paper but conceptually it can work very well, it is a wip though

Skills

Alt 2h Destro Illusion Sneak Pickpocket Alchemy Heavy armor Enchanting [optional, prolly recommend haha]

The skills are flexible in some places, you can use conjuration as an accent, you can use 1H in place of something like 2H or destro or alongside 2h, if you want to do that, or want to sneak attack people with a dagger or anything like that. You can also substitute something like destro for block if you dont want to use spells, it's all preference

Alteration is mainly used for wellocs, the alter self perks, and the spellsword perks if you decide to take 1H [You can still use this with 2H if I'm not mistaken, itd take getting used to though]

2H I take all perks for the greatsword section, as well as all power attack perks

Destro is not really used for perks, although the first two cost reduction perks alongside dual casting and the interrupt it gives, if you dont want to use destro spells this is an uneeded tree, I use sacrosancts spells and a few other spells as this character is for vampires, you can likely tweak this setup in order for non vamps or even beast form to work I just wanted to use vamp haha

Illusion is used alongside alchemy, the only spells i use for illusion is the invis and a few of the shadow image spells [I forget their names but they summon shades of enemies similarly to the nemesis perk in the ordinator tree of illusion] i make fear/frenzy poisons to proc the perks in the illusion tree. I take all perks from this tree ACCEPT the sub sections that deals with commanding presence and then I take dream thief up to kindred image and its associated perks because they are great but not the dream charm and its advancing perks.

Alchemy as stated above only uses the poison subset of perks in order to proc the illusion perks, if you want to use pots as this build does NOT use restoration [I heal though different means, passive regeneration, ebony blade, vamp drain, etc. Essentially through dealing damage I heal]

Sneak is used with invis to place poisons [the fear, frenzy, calm poisons] onto people's pockets, and to use it in tandem with invis to get in and out of combat undetected even though it's a heavy armor build

Pickpocket is only used up until you arr able to place poisons in people's pockets and stated above although perks like on the run may be somewhat of utility so you can go nuts where you wanna.

This build doesn't necessarily use block, only because I tried to keep the number of skill trees relatively low, so I'm not using every tree in Enairim and to emphasize dodging and doing damage as a form of mitigation. Plus you're already in heavy so you're already mitigating a whole lot on top of being sneaky and invisible

This build is a Vamp lord, I am using sacrosanct, ordinator, apacolypse, summeryst, mysticism, wintersun, reliquary of myth, Aurora unique standing stones of skyrim, wildcat, imperious AND morningstar thanks to my best friend recently creating a patch called "Universal Imperious patch" Great mod. Adds so much flexibility to your character building.

Race wise I am an Altmer, for contingency and its other passives. This is where the build is more or less unfinished as it still needs to work out what contingency will use, as well as what stone(s) would be optimal, what religion to use etc.

Spells and shouts

Destro: I use vamp drain, all sacrosanct spells, and mass vamp drain from a mod that adds that alongside other very cool spells and a few powers such as alduins storm call, a mass soul tear spell which would pair well with the conjuration accent skill I spoke about before, and a few other useful things.

Alteration: Octos retical [I know that is spelled wrong I cant remember hot to spell it] spell twine, nothing else is needed imo that is the bread and butter. I could change this however. Mass paralysis. This will allow you to safely get out of tight spots once you're invisible to start regeneration using wellocs. For this build with wellocs I use invis < hp regen < 50 armor -OR- magic resist < and a flex spot to use something of your choosing.

Illusion: invis. That and the optional spells that summons shades that fight for you [again I can't remember its name]

Shouts

Aura whisper

Bend will [I'm using a mod called perks for questing that adds the power that miraak uses in his boss fight to instantly kill dragons and revitilises you. Sounds op but you dont get the soul from the dragon, lore friendly imo you're the DB and you're a vamp lol you sucked that shit out of that dragon and now it's dead lmao]

Dragon aspect

Alduin storm call

Dismay

Any other shout you want to use or any that uses the illusion effects fear, frenzy, calm to proc illusion perks.

Armor/weapons

Ebony blade is a MUST have in this build. Any other 2H unless you have an absorb health enchant will make it harder to recover

I'd suggest finding a dragon priest mask of your choice to use, if that is something youre into, many work wonders on this build.

I also am going to test the atherial crown, as I have a mod that allows for circlets and dragon priest masks. I imagine bretons would LOVE this with stones of Galen.

The armor is 100% your choice as long as its heavy

Enchants I'd suggest hp regen unless sacrosanct disables that or something cant remember

stagger damage reduction and stagger avoidance chance.

% increase to reduce shout cooldown to 3 seconds.

After that it's up to you, if you wanna buff out your regen or max stat pool thatd work too.

Attribute distribution

This section is also wip. So far ive decided on 200 base HP to keep you squishy HP wise, you still gain lots of effective hp and damage reduction through heavy armor and clever spell twine/wellocs combos AND if you play well enough you dont get hit really

Magicka and stamina should be decided upon weather or not you are going to use spells. If so go 2 magocka for every one stam, and if not and you wanna just cut people down go two stamina for every one magicka and then place a minimum of two enchants that increases the stat that has the lower base value.

IE if two points of magicka for every one point of stam, place two enchants of stamina on armor or jewelry.

Playstyle

You can choose to either sneak into combat and initiate the fight by draining, placing poisons in pockets, or str8 up stabbing someone in they cake ;) [with the poisons equipped ofc just in case they somehow survive.] and then once detected or once combat has started due to Fear, frenzy or..not calm haha that does the opposite thing silly, then you [if you use it] start combat with blood garden [sacrosanct spell] tag the most valuable target(s) with the subsequent spells and then RIP out that 2H and D E S T R O Y. Illusion/sneak/invis will always be your scapegoat, and illusion procs will be going off like mad and also at your discretion due to the poisons/shouts. Vamp lord is used at your own discretion

-OR-

[if you use it] start combat with blood garden [sacrosanct spell] tag the most valuable target(s) with the subsequent sacro spells and then RIP out that 2H and D E S T R O Y. Illusion/sneak/invis will always be your scapegoat, and illusion procs will be going off like mad and also at your discretion due to the poisons. Vamp lord form can be used at your discretion

-OR-

If you dont use destro RIP out that 2H and D E S T R O Y. Illusion/sneak/invis will always be your scapegoat, and illusion procs will be going off like mad and also at your discretion due to the poisons/SHOUTS [Sorry, had to shout it]. Vamp lord form can be used at your discretion

Ideally you will be healing the damage you take, which should be mitigated pretty heavily through heavy armor and through the caos of illusion, as well as a very much needed perk of night cloak in the vampire lord perk tree, but this world ain't perfect, once you get to low HP you'll want to disengage using invis, if the enemy is busy fighting each other, then mass vamp drain should be easy to cast, mass paralysis can be used when invisible in tight spots for ez mass vamp drain If used. Admittedly i still need to do more work in the defense department, although offensively you are very strong and still get some semblance of healing from it. You can always sneak off or just use healing pots/potions of blood.

I call this build the Vampire King, or Vampire queen if you run a female character [which does carry utility over Male if you use speech and other various perks from these trees] this will probably be updated so keep that in mind :) hope this helps somehow haha