feature-request seems to be the most popular tag for it, so I'd suggest to use that (I'll add it to the contributing file).
The main reason that is written in the contributing file is so that developers don't spend hours adding a new feature only for me to say I don't think it should be added. If you post a thread for it here, we can discuss if it's a good idea and how the feature will work.
I will also likely continue Gideon's trend of posting a question here asking for feature reqeusts for the next version (i.e. "what do you want in Q2A 1.7").