That could be an idea I can appreciate, personally.
But, if the thread on carrying limit is any indication, I still the whole XP calculation is becoming a little passé, giving way to Milestone XP or Story Milestone.
One way I could see is if the A5E as some sort of metacurency. I'm partial for stacking Inspiration and having the party share a pool. This way, the DM could also have a ''pool of Inspiration'' that can be filled by certain method (Rolling a 1, PC suffering a crit instead of the +damage die, falling to 0 etc) like when the PC take a short rest, the DM add 3 Inspiration to its DM pool, 7 for a long rest.
That way, if the group rest too much, the DM will end up with an awful lot of Inspiration to give the players disadvantages or his monsters advantages.
But metacurrency in RPG are a really big point of contention in the community.