For its weight class I consider the Centurion the perfect medium mech, and it is on my rather large list of auto-include mechs to pull from when building a lance.
It starts with the AC 10 and LRM 10 which gives it good damage at long range- so it has support to add to other mechs on the way in, or it can hang back and do the long range thing for a bit thanks to its armor. Two long range weapons means it has the redundancy to at least hit with one if we can control the movement and cover modifiers.
The LRM also means it can play the indirect fire game. As we move to medium and close range the AC 10 can still put out PPC like damage minus the heat, before closing to use the two medium lasers at medium/close range.
Take it to danger close range and we have the Ac 10, two medium lasers and a fist for physical attacks. Only drawback I see is two ammo weapons on a medium mech/armor might make one sweat a bit with ammo explosions when/if damage goes to internals.
Is there a better matched medium mech? AND the battle value is under 1000 (945) on this mech, which saves a ton of points vs. what it can do/what you get.