For those that don't have access to Lamannia, the preview of the Epic Destiny Past Lives has just gone up on Lamannia.
Each sphere has a choice of 3 Past lives Toggles that you can have active.
Passives are the same for each Feat in the sphere, but the toggles are different. So in theory you could get the passive effect x9.
You can have one toggle active from each sphere, plus one from iconics, so that's an additional 5 toggles active that should stack with everything.
Not too bad.