Of course. I had actually been considering a build like that. I was even mulling over something extreme like a king crab with 5-6 AC2s ! Just park it on a mountain top and rain headshots all day
The KGC-0000, the only KGC variant in BATTLETECH, has 2 Ballistic hardpoints.
The only 'Mech that can boat ballistics is the JM6-S - with 4 hardpoints, two in each arm - which has 39 tons of space.
4xAC2 weigh 24 tons, leaving 15 tons for ammo, HS, armor, and possibly backup weapons and JJs.
Priority #1 is ammo. One ammo bins gives you 25 shots. I wouldn't want to go into battle with anything less than 3 tons of ammo for 75 shots, because I'll be firing 4 in every round of combat, and in a protracted battle I
still might run dry. That leaves 12 tons for HS, armor, and backup weapons.
AC2s build 5 heat each. The engine can sink 30, which makes additional HS unnecessary. So, 12 tons for armor and backup weapons.
10 tons of armor is nothing to sneeze at, and would be what I think is the minimum for this build, so let's start there and come back at the end. With 2 tons left to use, it's all up to personal preference at this point.
If you love JJs, they're going to cost you 1 ton per; for traversing elevation to pick good sniping perches - and with 4xAC2s, that's worth serious consideration - then 1xJJ would be a good investment, but 2 would provide you so little additional functionality it wouldn't be worth it. Round out with either 1 more ton of armor, or 2xSLs just in case something gets within your minimum range.
Or perhaps you like the extra punch of MLs. 2xML and 4xAC2s would build 40 heat on a 150pt alpha strike, which is barely worth a mention and easily manageable. If you want to play as a 2nd line skirmisher then you could use those MLs to great effect, and they would also keep you more useful in the fight if you happen to run out of ammo.
4xAC5s would weigh 32 tons, leaving you 7 tons for armor, ammo, backup weapons and JJs. You'd need at least 3 tons of ammo, leaving 4 tons for armor. With 3 different ammo bins, and without the safety that the extreme range of AC2s provides you, I don't think you could make this viable. 3xAC5s, on the other hand would be.
3xAC5s would weigh 24 tons, same as the 4xAC2 build. Everything I posted above would apply equally here, with a few caveats. Running 2xML and 3xAC5s would build 50 heat on an alpha strike instead of 40, and you wouldn't cool at all when firing 3xAC5s, so your max DPS isn't sustainable for as many rounds; however, your alpha strike is 185pts. So, if you like burst damage and don't mind spending a turn to cool down, you might prefer 3xAC5s over 4xAC2s.