clearance-wise the widest I can go on 700c is 40c (according to ritchey website), the tyres on it right now (soma cazedero at 42c are a good compromise between mountain-y/gravel-y tyre and road) with options to go wider..
what's the risk of a low BB? (other than hitting shit)
May I ask why this is running 650b? Looks like there is plenty of space for 700c and the bottom bracket seems to be quite low with this setup.
Bike looks very good regardless!