Wow this is incredible.
I don't see why you need to decide between a high or low base. Isn't the entire point of the legs so that the base (or the wheels) can be lifted over obstacles?
I'd love to see this built, but I'd like to recommend that you do it on a FAR smaller scale. This could very easily become a $20,000, four-year project. A pretty hefty burden if you aren't working as part of a team…
A really cool prototype would be to attach wheels to the legs of a
lynxmotion Hexapod.
This would provide you with a sturdy mechanical base and a "brain" to boot.