Are there any mechanical implications, short of the fact players can heal more on a short rest, to a house rule allowing them to restore all their expended hit dice after a long rest (instead of only half their total number of hit dice)?
The party recently lost their Cleric, so I instituted the Healing Surge optional rule (DMG, p. 266-267) to allow them to spend Hit Dice as an action in combat to heal themselves. They use this option more frequently than they took short rests prior to the change, but they struggle a bit since they only regain so many hit dice after a long rest. (Currently Level 6).