Ys music slaps (except Ys V... hopefully some day we'll get a proper port/remaster of it).
Following the thought expressed here a few posts earlier, I too have come to think that falcom could be getting its chance in the SSBU DLC.
1. It would be a Company bringing in the main character of a franchise that's never been represented in Smash.
2. Ys has a long running history as one of (if not THE) pioneers of the Action RPGs (oooooh Ys so goooood!)
3. Adol (depending on what game(s) they would use to create his moveset) could be a fun character to play as. The more recent releases have added the Flash Guard and Flash Move mechanics, making battles against enemies really fast-paced and engaging (and rewarding once one masters these two mechanics).
4. Did I mention Y's music slaps (HARD)?
5. It would help bring awareness of the Ys series (and other falcom IPs via Mii Costumes, and music perhaps) and could even serve to promote Monstrum Nox (although it already released, but the game's localization should come eventually).
Just the thought of having Adol finally meet Link in battle, and on top of that Cloud as well... it would be crazy. Fingers crossed ladies and gents.