I think it'll be interesting to see which design primarily informs K. Rool's appearance in Smash. Given both he and Isaac haven't been seen in many years, and the last time neither had their most iconic aesthetic, it may be useful to gauge how Isaac gets implemented. Whether they go for the Rare-era dark green and gold (as the costume would seem to imply) or the post-Rare lighter green and yellow-ish.
Frankly I can't imagine they don't go with Isaac's GS1/GS2 look, but them updating it slightly, or incorporating elements from adult Isaac or Matthew... that I could also see. I mean Ridley does seem to be a more original design, though harkening back to his older appearances over his newer.
And fwiw, Inkling does take from Splatoon 1 over Splatoon 2, though in addition to being the more iconic look, that's likely also due to timing, given the general lack of Splatoon 2 content.
As for clones, personally I don't even think that far ahead. I'm not going to start asking for seconds while I'm starving over here.