Speaking of Crono's magic, I have a crackpot idea. Make Swallow boost magic instead of speed.
When you pick between the Swallow and the Safe Helm, Swallow is almost never chosen outside of possibly speedruns because it peters out as soon as the Ocean Palace is done. Safe Helm ends up being potentally the best helmet in the game (it's usually that, Haste Helm, or Vigil Hat for me). One way to make Swallow not completely outclassed by Shiva Edge and Rainbow is to make it more useful, one method which would be to give it the near unique (Red Katana, Rune Blade on Frog) ability of boosting Crono's subpar Magic stat. This would make the weapon more useful against certain encounters, therefore prolonging it's usefulness.