Thinks that help with base destruction:
If there is a light, on the building shoot the light. Often with towers some top floor bit may still be intact. It is silly.
Punch through walls. The hotkey for punching is 5 in most loadouts (provided your mech has arms).
Use Jump jets to jump onto stuff. Mechs weigh a lot and that will damage buildings.
If bombardment is an option, take it. It won't help all that much, but it can knock out about 20% of a base.