They should start off using Shadowbringers as a base, where you got to choose between doing the Field Operation or doing old content. However, this time, the Field Operation should be the slightly more efficient way to do it (ie. guaranteed drops from Skirmishes and CEs, random from old FATEs or content).

The Shadowbringers method also made it so if you've done certain steps once, you don't have to do them again. This should be done as well, so that people who do repeat relics have to grind them, but so that it's not too tedious (for example, people told me they had to farm DR 100-200 times to get all relics, no joke). Doing it once for each job is reasonable, but hundreds is ridiculous.

The only other difference from Shadowbringers is that methods that are not going to have longevity need to be taken into account, such as the lack of people doing DR. For situations like that, the method would need to have an additional way added such as farming skirmishes or CEs, or making them drop from, say, DR Savage bosses since discords actually do that still.

We also need to consider that the players that "get all relics" will have proportionally more work the more jobs we get, so the percentage of the grind for repeat relics that is made a one-off quest will need to increase with the amount of jobs we get, to balance tedium.