What problem does this feature solve?

It will be great if defineComponent can return a component with correct vModel prop according to modelValue type

What does the proposed API look like?

just use existing defineComponent, but prop "modelValue" shoud be mapped to ”vModel"

Regarding the type of TSX supported by jsx-next, you should submit the issue to the correct repo. BTW, you need to provide as detailed information as possible, preferably with a demo.