OMG I love this idea.. I must say one of the single best ideas for end game ever.. I have a EoT which has only served to be a pretty ornament along with some other nice stuff like 3rd Floor IS stuff that I had to wait to be able to use till later.. The one area of concern is Tier Armor I would "HATE" to see it reset and or become unusable until endgame again.. however with the new Penultimate its a feasible option.. The AXP staying is a must.. This is a great idea..
I would suggest something like an auto-scaling form of Tier armor/symbiants that are installed at the time of "rebirth" or giving a "reborn" some other special enhancements.