I was was thinking that now (Mod 6) might be a good time to reinstate the bonus xp counter. You know, the one we used to have that let us switch an enhancement around before the revamp of enhancements? It would only start tracking your bonus xp when you cap, and would wipe when you level up. My idea is that after you accrue a certain amount of bonus xp, you can go talk to a trainer for a special reward. For Example:
250,000xp= Unlock a 3 part quest chain, that is a level 16 quest. These quests would yield no xp, loot, or favor. The only reward is you unlock a single npc. This npc could be a tattoo artist, barber, blacksmith (to reskin your armor to something more desirable,) or a mage that can combine any 2 like items (boots, gloves, full plate, short swords, etc) into one and bind that item to you.
750,000xp= 1 extra permanent enhancement point.
1,000,000xp= 3 extra permanent skill points.
5,000,000xp= I full respec of spells, alignment, character appearance, feats.
10,000,000xp= 1 full character reroll. You would be allowed to change everything about your character, except for the name, with the addition of a few more build points (2 maybe?)
The numbers are high because at cap xp is very easy to come by, but ultimately the actual values would be up to turbine to balance.
Just one idea for all of this wasted xp we earn while capped since we don't have crafting.