Shroob
Sup?
I definitely agree.It'd surprise me as much as getting a Valve or Blizzard character. I don't think Nintendo would opt to add a third-party of such uneven global recognition.
For better or for worse, Smash inclusion isn't predicated on any of those factors though.
Although I personally love Granblue(It's in English, yay), the game is pretty unknown outside of its playerbase, and Japan in general.
Outside of cameos in both Shadowverse and Dragalia, Granblue isn't known in the West, though I'd wager at least half the units from Dragalia are recycle characters from Granblue.