As a Novus owner (working towards Nexus and would have it by now if I didn't wait until ninja release to upgrade my MNK from animus to novus, I was holding all the Alexandrite and materia incase I liked ninja more.)
I would like to see them reset it all, perhaps make the final stage before expansion a nice glamour piece for the job. It's been a long grind and I don't intend on doing any of that again to just get to the start of the new expansion weapons and I think that would be what the majority would see. New jobs like DRK would never get relics because of the stupidly long grind just to get to the point where you can start your level 60 relic.
Perhaps continue along the path of slowly easing the difficulty of each stage every new patch and then when the entire questline from original relic - final piece at level 50 is almost trivial have it become a prerequisite to the next part of the new relic.
For instance we are currently at 2.4, 3.0 will be the expansion and the "end" of the current relic
In 2.4 Atma was made simpler
In 3.0 Animus books could be greatly reduced
in 3.1 General progression by this point should of made materia teir 1-3 extremely cheap and alexandrite easy to obtain (even perhaps sold by vendors?) Considering level 60 equipment might not even use it.
In 3.2 make light rewards bigger / target number smaller
In 3.3 make final stage/s easier
In 3.4 require New relic to be combined with old relic (fully upgraded).
This then doesn't remove all the work done by the previous generation and doesn't force a massive barrier to entry to newcomers to 60 as by 3.4 content will have matured and it will be a way to reinvigorate old content. Since the questline has been nerfed to something that can easily be obtained in a much more reasonable timescale it would take no longer than the usual single stage of relic grind. This would also allow people to add their Novus materia stats to the new relic.