It is possible to edit anims.j2a to fit our specifications, yes, with the one major flaw (as I recall) being the inability to change the number of frames in an animation. You could definitely have a custom sprite set for an episode or something - FSP2 did/will - it just hasn't been done yet, perhaps because there hasn't been much of a need for it. It's hard to justify a whole new anims.j2a for anything less than a big episode or other project, and not many have been released, so it's totally unexplored ground. You could probably win hearts just with recolors.