I could take to the 3DS Panel de Pon group, gaijin though I am, and doodle some fan art. One person alone won't bring in any new fans, but it'd be new material for FYPDP at least.
Furil as a Lip alt with different voice clips and character model has precedence in SSB4 with Bowser Jr. and Olimar. It'd be more feasible than having all of the fairies be alts of Lip, like I brought up earlier in the thread, since both characters are flower fairies. For an Assist Trophy, I think they'd aim for one of the more popular supporting fairies (inasmuch as any of them are popular outside the fanbase) more than anything, like Flare attacking with fireballs or Windy using wind to push the fighters around.
Looking at Katrielle, I can definitely see how she reminds you of Lip. From what I've seen of Level-5, they seem like a good secondary choice to develop a Panepon RPG if Alpha Dream wasn't available, though it seems like they're as busy with Yo-Kai Watch as Alpha Dream is with Mario & Luigi...
Super Plexis looks like a straight-up clone to me, at least from what little dev stuff I was able to dredge up. The panel designs are just barely not infringing. It shouldn't get them in any legal trouble, though, because that would require Nintendo to publicly acknowledge the Panel de Pon trademark which haha yeah right. (The character designs honestly don't appeal to me as much as Panepon's do, but very few character designs do.)