Lilac was literally one of the most hype ones they did. Also Lilac is far from a nobody. Freedom Planet did really well, is already getting a self funded sequel, and may even be getting two spin-off games. The game is very popular and I'd easily say Lilac is more recognisable than characters like K. Rool or whoever else people want because she's showing up in a lot of things and because she's still relevant, not like a lot of characters people core Smash fans ask for. While those other characters are former C-listers fading further into obscurity, characters like Shovel Knight and Lilac are rising stars - the next generation's Mario or Sonic, if you will.
They need to do more characters like that, and put the kind of effort and creativity they put into Lilac's one into the others more often. It's also just really cool to see them get commissioned by the creator of the game the character is from, official model sheets and all, as it contributes to the quality of the piece.
Smashified's potential characters go further than speculation core characters and there are a lot of classics between echo chamber characters and two-game ponies like Lilac.
Relevancy doesn't and shouldn't contribute to Smashified (and to a certain extent, Smash) on its own as Banjo-Kazooie, Crash, K. Rool and the entirety of Mother were received really well, because they were so old (though not forgotten, there's a difference between old and irrelevant)
Smashified revived these characters by a bit by giving them a new render and putting them in the spotlight again.
Smashified's schedule is bi-monthly at best and there are a lot of All-Stars, even if they're outside of the echo chamber that could be featured, especially if they are actually requested by fans (I dunno if Lilac was)
Phoenix Wright, Professor Layton, Daisy and Waluigi (who, if we're going by recognisability, are shoo-ins) or more well known indies such as Quote.
Commisioned characters should be kept a special thing, execpt if they're requested as well.
EDIT:
Grunkle Ford is best Disney princess