Squidboards

It would be cool to see them as an echo fighter, but there's probably not enough ink colours.

I would very much prefer to see Octolings as echo fighters rather than costumes for Inklings. Heck, just split the Inklings into two characters entirely as well, it was done before and it can be done again. Having four character slots dedicated to Splatoon, all dedicated to the four player character types won't hurt the roster at all.