how to ask a question about a new feature

Hello!
suppose I wish to suggest a new feature X for a software or a forum like this (I mean in the "feedback/suggestions" area or something like that), which sentence would you pick among the following ones? (Please rewrite/add other ones as you like)

- "Can you add X...?"
- "Could you add X...?"
- "Would it be possible to add X...?"
- "I would like the feature X to be added..."
- "Do youn think it would be possible to add X?"
- "How about adding X?"...
- "What about adding X?..."

Can/could you also explain how these sentence "sound" to you, native speakers?

Have I (or at least, is it better) to add "please" at the end of the above questions? ("Can/Could you..., please"?)
Or maybe at the beginning ("Please, can you...")

Generally speaking, do the "can you..." forms sound too "informal" for a written context?

Is "Could you..." always considered more polite/correct?

Which is the difference (in any exists) between "How about...?" and "What about...?"

Thank you for any help!