Put twists of fate into the new system. Really. 1-4 slots that open up at 21, 24, 27, and 30. Each slot earns experience and "tiers up" from T1 to T4 over time.
Each slot can "twist" in a power from a power pool set by the devs, each ability related to an ED tree.
This would give the players back some of the versatility they are going to lose in the sundering of ED's, and it will give devs the ability to greenlight whatever powers they are OK with everyone having access too. Heck, they could even add back ability score bonuses for those who want them, with T1 ability score bonus being +1 and T4 being +4 to the respective ability score.