I don't think a 2-player only episode will actually take off. As not many people use multi-player on SMBX as it seems, maybe because they don't have friends but possibly also because it is a counter-intuitive system due to the limitations of the keys that can be used, making it hardly feasible if at all, unless joysticks or joy pads are used. I think a 2-player only episode is only going to get more hate than love and simply be ignored, not because of bad content but because of inaccessibility.
I would say only make a 2-player episode for SMBX 2.0 and only if number pad controls are made useable by either updates or Lunalua codes that may make 2-player more popular, otherwise it will just be ignored and lost among other bad episodes before it gets a chance to become popular.
Signatures are overrated.