EDs are powerful enough that many people recommend not TRing already because the gains are trivial compared to what EDs give. This would amplify that by a million for those that don't just immediately quit the game. For this reason alone I don't recommend removing our ED XP. Or, as one poster suggested (and I like) remove only the bonded (active) destiny XP, and give that destiny a PL bonus. That would actually encourage people to Epic TR.
But yes, at the very very least they need to preserve fate points and unlocks.