Ok, so here is an out there suggestion (and I can already hear the screaming…heh):
If I understand correctly, the game expects most parties to get 2 short rests between long rests. This means a warlock can use their entire allotment of Pact Magic three times between long rests in an ideal situation.
So, how about we leave everything about Pact Magic the exact way it is. However, instead of recharging on a short rest, warlocks get triple the slots and recharge on a long rest.
Right now, a 5th level Warlock gets 2 max level slots, recharge on a short. Instead, they would get 6 max level slots, recharge on a long.
The amount of spells they can cast should be the same, without the warlock being dependent on begging for short rests, so it shouldn’t step on any other classes toes. This still means the Warlock needs to watch their resources, but frees them to Nova along with the other characters if needed. And they won’t be hindered if they are in an adventure that makes Short Rests prohibitive. Also, it removes the need to invent new abilities like “Channel Patron” or the like.
Anyway, just spitballing here. But if I’m right, the math works out the same, keeps the Pact Magic flavour, and removes the recharge angst.