Crimson Longinus
Legend
What if there were only short rests, but the player decides what gets recovered on the rest?
For (early-idea) example, on a short rest, a player may do one (or some limited number) of the following:
a) Spend HD to regain hp
b) Recover HD
c) Recharge a class ability (or a few?)
d) Recover a spell slot (or more?)
e) Recharge a magical item
There would need to be some math involved to balance it, but one could see one player choosing to heal with HD, while another takes the risk to stay with her lower hp after the battle in order to recover a higher-level spell slot, and another player pours his essence into the helm of teleportation.
This would be even more interesting if characters could use their HD for things other than healing, like powering spells, etc.
What happens to long rests in a system like this? A "long rest" is essentially when you have enough time to chain a bunch of short rests together, so the DM handwaves it and people fully recharge. However, for people who like it, you could always be in a state of "not fully there" and so attrition is a major factor.
Sounds actually pretty fine, albeit it might be too fiddly for some people's tastes as they would constantly need to decide what to recharge. It would also need to be somehow scaling like prof bonus' worth of recharges or something, as higher level characters have more features.