I think this extension could possibly be a killer app. However i've been looking at GIT for SW dev and i think current HW dev design work is also highly non-linear. Thus it would be ideal if i make a change to both part 1 and 2 in checkpoint 1. And then change 1 and 2 again and snap checkpoint 2, it is quite probable that mgmt will ask for the changes you made to part 1 from checkpoint 1 and the changes you made to part 2 in checkpoint 2. Within reason it feels likely that i should be able to cut and paste the changes from both of these checkpoints to a 3rd checkpoint to more efficiently take mgmts' decision forward.
As another side note, i wondered if the tmz could be made multi-user in nature or have tmz inside tmz to allow explorations to take place at a system AND at a lower level point of view.