I wouldn't mind a grind for the Relic, but I would very much like for the grind to be a quantifiable one.
If they want us to do FATEs, do it like ShB one where you had to go do a total of 60 FATEs in HW areas, rather than the older Relics where you had to farm Atma's with such a low drop chance that people started having conspiracy theories about how their drop rates worked.
Any items that need to be bought, should be from the slightly more obsolete currencies... GC Seals, Poetics, past expansion's Tribal currencies etc. No need to tie crafters to the Relics as they have their own ones nowadays.
As little content that exists primarily for the relic as possible, as when the next expansion rolls out it very quickly becomes somewhat abandoned by Square and the playerbase. Future-proofing is important.