Having this game use “Online-Only” methods to unlock non-paid skins is an… interesting choice, that I feel won’t bode well in the long run.
Might I suggest you all should borrow from Melee’s unlocking method where there’s multiple ways to unlock something.
Example: To unlock the Abyss skin for a character you can either:
Reach Character Level 100.
OR
Achieve ‘Aether Rank’ for that character’s Easy, Medium, and Hard mode of Arcade.
This would give a material reason to play the Arcade Mode, plus allows players who might not have constant or stable internet unlock some of the achieveable skins.