There are quite a few replacement sprites for secondary characters in all of the DS CV games. It would be nice to see some replacements for Jonathan, Soma, and Shanoa. DPA has a good start with his Simon SCV4 Hack. But I feel like There should be another hack with someone as versatile as Jonathan who can use all sorts of weapons and skills. Nathan, Hugh, Alucard, that guy from Soul of Darkness... Well you get the point.
If you go check Work in progress site you can find my Richter story mode mod if you are interested. It's a mod that replaces Jonathan and Charlotte With Richter and Maria with new animations, new weapons, level editing, new music from other dsvanias and other games entirely. I'm also doing new extra character Simon Belmont to that mod.