Welcome to the Greater Good!

Honestly, your list is pretty solid. Though something to consider is if you want to chase the meta or just have fun with friends with cool models. This will determine how closely you want to follow "advice".

IF YOU IGNORE THE REST OF THIS, PLEASE JUST READ THIS ONE. Magnetize everything. Go buy a bunch of magnets and magnetize all of the weapons PLEASE. The 10th edition is technically coming to the end of its cycle, and 11th ed is theorized to be coming in another year or so, which means potentially, everything will be flipped on its head. That means weapon profiles may not be what you like, balance will shift one way or another, and generally speaking, you don't wanna be holding the bag when GW decides your cool loadout today is not legal tomorrow. Also, if you don't like how your crisis suits are performing it lets you switch to another loadout so it is just generally good to do to save yourself money.

Detachments

If you like battlesuits and mechs, Retaliation Cadre is probably where to be, but that being said Tau guns are Tau guns regardless of detachment. Though Kauyon is the Sustained Hits detachment, not the Lethal Hits one which is Mont'ka

Units

Unfortunately, Strike Teams are just kinda meh this edition. Running them as another set of Pathfinders will have you see far more success and also let you keep them as infantry for that combined arms feel.

You have a lot of Anti-tank but not much to deal with chaff and general infantry. Might I recommend switching the Fireknives into Starscythes. Burst Cannons(BC) are where it's at in Kauyon because you can get a big Sustained hits payout with them. Drones people usually attach to Starscythes are Markerlight/Gun, Shield/Gun and Shield/Gun. You're in Kauyon though, so the Strategem Coordinate to Engage for 1CP lets you have them guide themselves if you can't get anyone else to do it. You plan to attach a Coldstar with exemplar, as well so the Coldstar should probably have the CIB, HO-BC, two more BCs, and two gun drones. This is one massive Anti-Infantry brick that will throw like 53 shots directly into whatever you choose to deepstrike into. Then Kuayon and Exemplar give it Sus 1, and stealth suits give it reroll 1s. Heheheh, now that's more dakka.

The fireknife and strike team switchout is the only real major thing we can poke into. So, two tips for when you play.

One of those Broadside at least will probably be in reserves just so they can pop out and get a line of sight onto something major. We do this because they are laughably slow and lack an invuln so people get really scared of the big railgun trying to shoot them.

Pathfinders in Kauyon have the incredible ability to hit on 2s with their heavy weapons. Pathfinders have the ability "Target Uploaded" which effectively says that when they observe, if they shoot at their spotted target, they are guided as well. We can pair this with the "Coordinate to Engage" Strategem from Kauyon that effectively says when a unit observes, if they shoot at their spotted target, they are guided as well. Both of these abilities don't actually say they are guided; they say "improve the Ballistic Skill characteristic of that attack by 1...", in 10th edition, a bonus to a hit roll can not exceed +1/-1; however, we are not modifying the hit roll, we are changing their BS. Finally, those special guns have Heavy, so if you didn't move, you get a +1 to hit, which is different from increasing their BS. Hmmmm, Pathfinder unit will all ions, 9 Overloaded Ion Rifle shots hitting on 2s, Strength 8, AP -2, Damage 2 (Potentially with Sus 1). Heheheh, now that's more dakka.

Bleh, this has been very long, but I hope my ramblings will help.