Would these individual ideas be better asked as separate questions?

A request for arbitrary suggestions doesn't seem like a good fit for the question and answer format. I wouldn't know whether to interpret voting on the answers as a measure of how well the answer is written, or a measure of how popular the idea is.

If there is demand for idea generation, rather than questions about existing ideas, do we need a new Category where these will fit better than Q&A?

I think the recent individual questions about how a specific sport might be adjusted for low gravity are a good fit for Q&A. It's only this one question that I'm having concerns about. It seems like it might be better suited to chat, and then the ideas thrown up could become specific questions later.

I agree. Asking how to adapt a specific game to a new environment (such as a low-gravity environment), while somewhat broad, is still focused and answers can be judged with some degree of objectivity on how well they address criteria laid out in the question. However, a question simply asking "What are some good home games for people living and working in free fall?" is simply too broad to be a good fit for a Q&A format.