How easy is it to make the change, would you say? And interesting to hear.
Moderately difficult. There's no external way to do it, you need to install a java editor, download the sourcecode for MegaMek, find the classes for each weapon you want to change, and compile the source code.
There's also no central location to make changes at. The option that already exists to increase AC/2 and AC/5 damage by one? That only works for regular autocannons - LB/X and Ultras need not apply, because they use a different parent class.
What's HBS got their ACs set to these days? They seemed a bit excessive when I last saw them. Like "why would anyone ever use a PPC?" excessive.
I haven't played the Battletech game since it came out - it runs like molasses on my system. Assuming they haven't changed it since launch, here are the values:
AC/2 - from 2 damage to 5 damage, a 150% increase.
AC/5 - From 5 damage to 8 damage, a 60% increase
AC/10 - From 10 damage to 12 damage, a 20% increase
AC/20 - No changes.
For comparison between the AC/10 and a PPC, here are the stats:
AC/10: 12 damage, 3 heat, 12 tons and 7 crit slots. Range 5/10/15. Requires at least 1 ton of ammo, and 3 heat sinks to be heat neutral.
Final values: 12 damage, 3 heat, 16 tons, 11 crit slots. Range 5/10/15 (10 shots)
PPC: 10 damage, 10 heat, 7 tons, 3 crit slots. Range (Min: 3) 6/12/18. Requires 10 heat sinks to be heat neutral.
Final values: 10 damage, 10 heat, 17 tons, 13 crit slots. Range (Min: 3) 6/12/18.
So yeah, I can see your point - apples to apples, the AC/10 is slightly better than the PPC. Except that it has a limited lifespan (add another ton of ammo? They now use near equal amounts of tonnage and crit slots), and has the penalty of having explosive ammunition, just waiting for an unlucky crit to turn your 'Mech into vapor. Because the tabletop is a lot less forgiving, and before the advent of CASE, your 'Mech will turn into confetti if its ammo gets hit.
Meanwhile, the Awesome is just happily firing away with its PPCs, long after the AC/10 has run out of ammo.