Continuity Issues
If we plan to have character skins for every continuity we need to solve the issue of inconsistent alt modes, one example being G1 and TFP Soundwave. I see a few possible fixes for this issue:
Alt modes primarily used in Ultimate Attacks and not for mobility (last resort super lame option)
Original Alt Mode designs. While this does mean we likely will not be 100% faithful to all continuities, it will help with game balance
Create entirely new characters for certain skins, but with the amount of times Hasbro as re-used an old name to save the trademark it might be rough
Other suggestions welcome