Add Legendary stat-swapping ability to ascended items and restore max stats to Exotic levels. This should help maintain current game balance and comfort treadmill-fearing players while keeping Ascended items a tangible and desirable mid-term reward to work towards.
Incidentally, Inscriptions are probably also a bad idea (relatively high cost combined with highly specialized effects creates a barrier to flexibility, even if the effects of the inscriptions are very limited). With the Living Story and important system updates revitalizing the game, the current Ascended tier is a devastating step back.
The ability to switch secondary professions after Ascending in Prophecies provides a neat lore parallel for the change.