Currently on Beta it is possible to craft Relics of the Past I-V for old professions. These change the level of the item, and may be used during crafting when old items are made.
If this makes it into live, this unfortunately means that auction house users will have to craft five times as many items using all the marks to accommodate for all the different levels. This would result in thousands more auctions for some players. Difficulties would be caused both for individuals trying to post so many auctions and the community as a whole because the AH API would be clogged up.
Here is my suggestion for the Relics of the Past. I think that these are actually a really cool system that is likely to offer players greater customisation options. However, these should not be put into the game as they currently are. I would suggest that instead of all professions being able to craft them, they should be made available only to Shadowlands enchanters to be crafted for all other professions. Further, rather than being used on items during crafting, these should be one-time consumables to be used on already-crafted items. If used, they should make the item soulbound and not able to be put on the auction house. Old professions should only be able to craft one version of any item, rather than five with different level requirements. If players wish to change the level, they should be able to do so making the item soulbound.
These changes would solve all the issues that I have discussed above.