Adding a second charge would be a great move as it'd help make assize quite a lot more flexible and versatile.

Sitting on a charge to use for as a healing oGCD wouldn't be a significant MP & DPS loss anymore (something which EW is going to make even more important).

It'd also allow WHMs to dump charges during DPS windows to help them keep up with the other healers a little better.

Win win all round, I can't really think of any other reason not to like a change like this outside of 'f healers' tbh.