-
First off I have zero engineering / architecture / building design experience whatsoever so take what I'm about to say as absolute pure random stranger on the Internet speculation and the furthest thing from a guide on digging up part of your house you could get.
I think that I've read that the external supporting soil runs around 45°. So as a starting point use that as a guide to the internal. So I'd work out the minimum head height needed. Then mark out where 45° from the edges down to that min height is on the ground.
That gives a rough perimeter to work out whether it's a potential goer.
Obviously before doing any work you'd want some proper advice.
Idk what your layout is, but what you can potentially do is dig down in the middle to give you extra head height - if that makes sense? Sort of like a channel.
Often you'll have wall storage or maybe a work bench, or tumble dryer, etc. so you don't need "real" standing height in those bits - just getting in/out and moving around to get to those bits.
It's very situational, but worth thinking about.