problem is that way later down the line, a lot of us here will already have established eidolons and kami... only ones that benefit the most from "lilim-like" effects are ones that can't make a team focused on one single element...
that's unless the translated comment i read was right and she does give a boost regardless of the team. cause if I read that right, no star SSR diabolos gives 25% to everyone if you run a team all of 1 element, and 50% if it's 2. 3 or more gets the full effect at 100%.
if that comment wasn't true, then she'll most likely be a buff slave like the lilims and tossed into sub eidolon slots if any...
honestly, i feel like the "lilim-types" would be more useful that way if they did work like that. Where you get a smaller effect if you have 2 total elements or all 1 element... but the base stats would still be an issue...
if your debuffs and such is already covered (and you actually got lucky enough to pull it off), the best (or at least one of the best) eidolon setup would be a maxed 100% eidolon as a lead and friend, with SSR dragoons maxed and filling the sub slots