It depends on the relay, some filter what kinds they accept but yeah, if you have issues there you can contact the relay maintainers and ask if they can make it work with your kinds.

Also self hosting it's pretty simple, you can also have them as a paid option too, maybe for a social integration too.

You should analyse your project closely and see if some kinds might be reusable without have to make new ones, it's better to use the power already at hand if possible, especially if you need to keep it working even if your app have downtimes or you want to interact with other type of content, that's the beauty of nostr.