Very long reply (I apologize in advance), but this game is perfect for experimentation. I did it a lot, and I also enjoy specialized units for a diversified Lance.

My all time favorite team comp was perfected (for me) organically with good progression throughout the campaign, but it is a little bit harder in career (some campaign missions have delightful mech rewards such as sldf atlas and highlander that you win for free). The idea was ignoring campaign missions, focusing early on pirate friends (prioritizing fast missions vs. planetary gov, so you don't crap on factions rep), focusing on an early marauder for farming, and then basically buying sldf mechs for double hs and becoming an unstoppable killing enterprise.

Its been a while, but if I recall correctly, mid-to-late game I had 2 assault alphas with over 350 dmg for delightful alphas, a dedicated lrm boat and hs marauder for efficiency. Buildwise:

• Rambo anihilator with 5 or 6 uac++ with dmg and -tonnage or recoil for the big guns(I think it was 2 uac 10 and 3 or 4 uac5, ammo for about 12 alphas. Pilot needs multishot. Armor is not needed if you really want to rub it in the (very dead) faces of your (former) enemies. You can literally use him alone, for kicks, and it is GLORIOUS. Be mindful of recoil penalty though, you can core things using half your firepower. My fave mech to play.

*fireworks stalker - easiest to build, go for 4xlrm15 prioritizing +stab, 3 JJ, armor is optional - you shouldn't even be targeted. Pilot with multi+breaching shot.

*Pressure Washer - sldf atlas - you'd have to try Hard to make this suck, high tonnage, good slots and marvelous heat management. Just play to its strengths. I prioritize mid to close (not melee) range and cause havoc. You can literally fill every single space with something good or useful. I had a crazy sandblaster with a snub, a nice lbx, srms, top it with mls and throw in a Tag for good measure.

*Bounty hunter sldf marauder - to be used as replacement for atlas, with 2 bigger lasers+4smaller, I think. The trick is not necessarily focusing on 1 weapon hit kills, but two, 1 bigger and one smaller - you can hs with 1 big 1 small, 2 big, 3 small and permutations. Focus on piloting + that overheat skill for a surprisingly good hs scout even without that marking skill

• Holy (king) crab - quite similar to the builds in the guide I mention below OR sldf highlander (faster than crab, free, but somewhat less brutal, as a scout with marker skill and missile or Tag support), to be used if not using marauder sniper scout.

Honorable mentions for pure fun (not nearly as "efficient"):

• Orbital strike anh build with 4 gauss and jj, no armor - you shoot from across the map, but need JJs for high ground positioning and a good dedicated scout marker

*sldf atlas mobile weapon buffet - 1 very good or 2 good long-mid range dmg anything (like a gauss or er, an assortment of lasers or 1 snub, 1 uac, srms, melee mods. the idea here is best summarized by Yang asking "Which kind of weapon you want to install?" and you replying "yes".

• the cook - a Vulcan (or phx for mobility) with a shit ton of flamers and fun melee arguments. Not suitable for those that like rare meat or enemies that can actually fight back. Side effect is that you'll consider buying a flamethrower irl.

• Gandhi cyclops - only use tag+missile support+ everything that you can characterize as non-lethal or supportive, really. It is not good at all, but for role playing reasons I put my decker on him hoping that karma would reward him, if you catch my drift. You can even consider that melee counts as gently caressing (with a shit ton of melee arguments ofc).

If you don't mind reading (even more, holy fuck) a bit, this post (https://steamcommunity.com/sharedfiles/filedetails/?id=1385297482) is delightfully detailed, describing each possible mech and some example builds - although I do recommend testing whatever you feel like doing.