Another batch of Ideas for you to ruminate over.
Mini Firetruck by LegoDragon213. This has 4P people, but I think it's a little large for that scale. Other than that it should make for good terrain.
Emissary by Legofire772. A sci-fi battlesuit made with an abundance of Mixel joints.
Microscale Jurrasic Park by Senteosan. I'm not normally a fan of IP tie-ins, but this could make some fun terrain for our mecha to stomp through.
Flying Mobile Frame Zero by DrJ29014. It's a set of Chubs. Get behind this people!
As always I've supported everything on this list.