I think if they want to strike a balance between 'you can farm every relic because you're a collector' and 'it's a grind worthy of a relic quest', the solution came with Bozja: The 'Blade's X' step required 30 of 6 different items, which came from either specific Alex/Omega/Eden raids or doing CEs/Skirmishes in Zone1/2/3 of Zadnor. This gives options, if you don't want to do Zadnor as much you can do the raids (I got a lot of my items by going into E12 a lot for the final TT card I needed for the Jam-On-Toast mount). Additionally, this step functions as the 'grind', but only needs to be done once. Every weapon after, requires a much smaller (by comparison) grind of 'get 15 memories', which you got 3 at a time from Dalriada, or 2 at a time (and 3 timeworn artifacts for a previous step) from Delubrum, so you could bash out two steps at once
So in current quest terms:
One time quest- Gerolt says 'We need 10 of each of these rare items WOL, they come from Bicolor Gemstone vendors idk how they got them but you need to buy them for us'
100 gems, 6 SHB and 6 EW areas, total of 1200 gems (or, 100 Gold ranks). This incentivizes farming FATES in SHB/EW areas, meaning it's a good chance to level any 70+ jobs at the same time. Formidable/Archaeotania/the Thav one/Chi are revitalized because 84 gems for a Gold rank. Getting rank 3 in some areas almost passively due to the grind.
Repeatable bit- Godbert says 'OK thanks WOL we now have the capability to improve the relic even more, but we need the rare final materials to do it and wouldn't you know it, Rowena's the only known source somehow'
Buy 5 SuperGoops (or whatever name) that cost 100 Astronomy each, or 300 Poetics each (or hell have both currencies as options, why not)
Each weapon to upgrade requires 5 SuperGoops, so in total to get all 19 relics you'd need 95 SuperGoops, costing 9500 Astronomy, or 28500 Poetics (or a combination of the two currencies). Poetics as an option reincentivizes doing non-max level content like Eureka, MSQ roulette, etc, and allows people to earn relic progression on non-capped classes (level alts AND get relic progression via Levelling/Alliance Roulettes? Yes please)
(prices can be adjusted for balance)
People who want only one weapon (or one role, ie all tanks) would do the grind, and get their weapon, and it'd be a satisfying 'I worked to get this and now I have this, dopamine obtained', but those who want all 19 would still be able to 'reasonably grind for all 19'. As it stands, the current total tomes needed to get all 19 weapons up to current level is 4500x19, or 85500 tomes. I would be fine with grinding out 85k Poetics, since we can get 400 a day via MSQ roulette (and get loads from other sources like WT), but Astronomy? No thanks, I'll just wait till 7.0 when it's all shifted down to Poetics. I take a small amount of solace knowing that, making the current relic cost Astronomy, means that it'll cost Poetics in the future, and that when that day comes, the extreme amount of Poetics needed will re-incentivize one of the best 'spammable sources' of them: Eureka