If I pay to support a game, I can request content for my favorite character and I only want content for my favorite character
Typically when you pay to support something, you partake in a type of governance where you, as a part of a collective (i.e. you are not the only supporter) get to _vote_ for certain content, which IIRC is typically done through Patreon and is limited to what the developer (the Majalis duo) put up to a vote. A person who has control over the creation of some content would be someone who _commissions_ work, which is would be different and far more expensive than being a supporter. Essentially, being a supporter provides these benefits for you
1) You get to 'feel good' in that you take some small part in supporting the development of the game _financially_
2) You get to feel as if your vote matters (more than it does) by partaking in some type of governance, typically, by voting in some poll wherein the majority select vote may not be what you have wanted, but your vote does at least count in some way.
3) You get access to parts of the game that are unavailable to others, i.e. the Story Mode (not much content available but pretty darn good addition, some very nice sex scenes) and Cheat menu (makes the game more bearable given you can 'cheat' the RNG and random encounters).