The hunchback, Centurion, and Enforcer are going to be your best bets for heavy hitter in the mediums. They hold (slightly) more than the marginally faster 55 ton designs.
I had good luck with an ac20 Centurion with SRMs for backup. Or the AL allows some decent laser/ppc builds backed by missiles.
I also had luck with an enforcer with an ac5 and a bunch of med lasers and heat sinks and jump jets.
Hunchbacks are always effective with minimal changes.
I’m not a big fan of the ac10, you can do marginally less damage with the ac5 and save 5 tons (since you’ll need 2 tons of ammo for the ac10). And if you can fit an ac10 you can usually free up 2 tons and jump to the actually impressive damage of the ac20. And range doesn’t mean much, so that doesn’t hurt it too much.