I think if you're making a jam about disability it's really important to encourage developers to make their games accessible, so disabled people can actually play them. There's various guides to game accessibility around the place, here's one I wrote about VNs specifically https://spiralatlas.github.io/making-your-visual-novel-accessible/

Not every game can be accessible to every person, and "accessibility" isn't a clearcut thing, so I'm not saying you should make it compulsory. But you should suggest that developers seriously consider making their games as accessible as they can.

I'd also suggest clarifying what exactly you mean by "content warning", since that is also not clearcut. The number of things people CAN warn for is endless, what specifically do you consider necessary to warn for? One I'd suggest is flashing lights, which is a major accessibility issue.