Ok, before you laugh me off the forums like I may well deserve, I do have a fair bit of reasoning for this suggestion. As its only use is to level with, exp becomes useless at the level cap…this is of course entirely to be expected, but has a couple unfortunate results.
The most obvious is that the death penalty no longer has any meaning. Avoiding death is a major part of the game while you’re leveling, because dying too often can significantly hamper your progress. At max level this is no longer a concern because levels cannot actually be lost, for good reason of course as that would cause a wide variety of problems.
Less obvious but more significant is a loss of the feel of progression you have had throughout the game. Several quests no longer offer anything meaningful, which makes finishing whatever you have left of the campaign feel less rewarding. On top of that, the periodic and predictable gains you’ve had from leveling no longer come. While you can still improve your character via gear drops this is entirely random, whereas levels were something you could see that you were building toward.
This idea is an attempt to remedy both issues with one mechanic. If exp can be spent on gear, then you get back that feeling of constant visible progress toward improving your character even at max level. Death also becomes relevant again, as exp loss is an actual setback if there’s something to use it on. Finally, it still keeps gear collection tied to the core mechanics of killing monsters and doing quests, as this is how you get exp in the first place.
There, that’s about all I have to say. NOW you can laugh me off the forums like I may well deserve.