Reach from the BB to Handlebar grips could be kept the same.
Instead of having short frames and relying on long stems, wouldn't it be better to lengthen the front of the frame and use a mega short stem, along with a taller headtube, to achieve a similar BB-to-Handlebar Reach?
Some thoughts:
More toe clearance relative to the front wheel
Significantly reduced chance of bashing knees on stems.
Longer wheelbases across the board:
Can do bigger wedges and also be more stable overall.
Also will allow bigger Up-To-Fronts, Taps, Hooks, etc.
Shorter stems = hands closer to the steering axis
Even High BB frames will be able to bunnyhop and manual better than they currently do.
Long stems/Cantilever stems are pretty horrible to do Bunnyhops & Manuals with, and also are more prone to jackknifing:
Imagine rolling at a slow pace, then suddenly the stem jolts sideways 90 degrees without warning and you go OTB and get tangled up with the bike - has happened to me, and I know it wouldn't have happened with a shorter stem.
Long stems place too much weight on the hands too, so your hands/wrists/arms are more likely to go numb than if you were using a stubby stem with hands super close to the steering axis.