Similar to Legendary Potential, set could have Unique Potential.
or a mechanic allowing the set item to be crafted.
It would be cool to somehow slam a unique onto a set item of the same type.
Or maybe it could be an affix swap.
It could be a new Dungeon, similare to Temporal Sanctum, allowing to put a Unique and a Set item into an altar.
The result would be the set item with 1 of his initial affix swapped with 1 of the unique affix.
There could be a Stage 1 for the Dungeon to target Implicit affix.
Stage 2 to target affix, etc.
Each try would consume 1 Unique Potential.
So you could try a second time with a different Unique for example.
This suggestion would be counter to the design choice the devs have of making set items distinct from unique items. Unique Potential, while slightly different, would end up making set items too similar to uniques.
Set items are also being worked on so that they will have more of place when pushing into endgame territory. I don’t think this is happening by 1.1 since there are things higher on the priority list AFAIK.