When leveling up, one's energy is completely regenerated. One of the fun parts of this game has been timing this to coincide with the end of an energy dump during a raid or incursion/portal.
But then you hit the level cap and this part of the game disappears. Part of the fun dies. But perhaps it doesn't have to...
When a toon reaches the level cap, they could continue to earn fake XP toward a "next level." When their XP bar fills up, when they reach this "next level," they don't actually gain a level (after all, we want to preserve the level cap), but their energy bar completely refills, and their XP bar starts refilling again from zero.
It would be like continuing to earn new levels, except for three things.
1. Since they aren't real levels, stats and might are unchanged.
2. Since they aren't real levels, it doesn't show how many fake levels the toon has earned.
3. If a future release raises the level cap, toons that have earned fake XP start gaining real XP from level 30 (or whatever the cap was).
Feel free to email if anything above was unclear or leaves implementation or balancing questions.