1st: we should be able to pick the kind of resistances we want. Seeing this sets, they could give the posibility of pick the resistances in pairs: for example, elec/water, fire/wind, curse/light (ofc the combination could be different but the 3 big ones should be separated).
They could do it with the

2nd: since each armor piece have crit/skill crit, cad/scad, and 2 resistances, the player could be able to pick wich of both want. This selection could define the bonus of the set, but that could be complex. And also would define which stat rise (in the case that those stats are able to be rised in that specific set, ofc) when the player reinforce that item.
In the case that the stat selection define the set bonus, then the only way to make it work would be that each armor piece should have the same setup to give the bonus. And the set name instead of said Str, Con, etc, would have a code between []. Such a code could be defined by the 1st letter of each stat name, for example, the set [SSSE] would be Strenght, Skill Crit, SCAD and Elec. In that case, they should find an alternative letter for Wind or Water.
3rd: the selected stats could be marked (in each item) with a small circle, and the stats that can be rised with the reinforce could be marked with a small star.
Such system wouldnt add much more difficulty to find the components, since would exchange the Exekyon Controlled Element Xeon for 3-6 Exekyon Controlled [Element] Xeon (if the drop rate isnt bad, then it shouldnt be a problem). What gets a little more complexity is to make the item, but the end result would worth it.
This idea could use some refining to make it more simple, and ofc all suggestions for that, and even alternative ideas, are more than welcome.