honestly.., The book Phase would be much better if you can buy all the books at once.., or at least let us buy one if each type..,
so instead if each one by one..,
it's more In phases, 3-4 book phases.

But As Someone who Did All the Relics.
it's really just if the relic matters at all for you, rly.
<now if you add alts in the matter, there should be a new final step added. Like linking a certain Crystal to all Relics, which should lessen and alter the requirements for all Expansions, including ARR relics, accountwide, unlocks maybe for alt characters>
as for ARR Lights, just make it more obvious which duty has a bonus, by having it notify in the system, but in a not obtrusive way, like when it notifies you when you unsync in chat.
it's ridiculous to expect people to sync the dungeons for Relics at all nowadays and would be backwards.

tldr: For ARR[though I can careless, and tbh it's the effort that adds worth] Make it so you can obtain all books, or obtain all the books of the same phase(1-2-nether <except for the last single one which should be taken anytime>) and work on them simultaneously. which would drastically kill the dread and time consumption. and make it obvious which duties offer bonus light at any time.
[but personally, as someone who has all Zeta, I'd like this to apply to accountwide. like of you was to link a certain orange crystal and "soul bind" your gear to the WoL/D. which any alt you could have. also is, to reducing time getting Relics on alts.]

Can't say much of Anima, despite having all the Relics as well.[never melted my zetas, seems ridiculous to do so]
Gathering the ingredients was kinda annoying but not as much as other stages. one weapon also had its states fd up, but eh. Anima had a much easier time to deal with. though I guess more reminders/clearly indicators of what stage you're on. as its easy for many to forget to get a certain item, or talk to a npc before gathering, light etc, etc.
Lots of prep work, but you miss a step after a long time grinding[if you really didn't notice] or have to leave party after first run, cause you noticed it early.

<same as before, add reduced requirements for accountwide>

Eureka/Bozja only need a few adjustments.
asides accountwide, which would be kinda different than the other Relics when it comes to unlocking. but for eureka, allow trading in items you don't need any longer for other materials, like feathers for protean/anemo. or increased chances of 5, instead if 2. as well for the other zones respectively.
as for bozja, a- the more of an item you have, the more you accumulate system.
would reduce memory grind for those who do all at once. whilst keeping it normal for those who do one at a time.
<though again, these changes only seem worth only benefiting alts in the end.>