This is a project of some ambition... I like it. & I can definitely understand the appeal of a wargame that needs less space.
I think my first tip would be to get a pair of tweezers, maybe the cross-locking sort, & put some packing foam (or similar) around the jaws. Big hands will then be less of an impediment (gross motor skills are beyond my solution, sadly). I'd also advise using more smashed walls, or barn doors, than regular doorways as entries to buildings. They'll just be that much easier to use...
Otherwise good luck with the project! You seem to have made a good start with those designs, & I look forward to seeing how it comes on.