The way I see it you are a builder and you are good at it. So that is what you should be doing since that is what you enjoy and there is indeed a lot to do on your roadmap. I think it would be best if I and others (e.g. @oryhp @vegycslol, advice on how to deal with security) pick up the proposal and extend it by thinking of how a Grin HD wallet and one time use addresses should look like and work towards and RFC.
I do not think the RFC is something you should spend to much time on although your practical mindset and feedback will be very much welcome. Once there is an RFC, it is up to you to apply for funding and build it since you and @david are the only once capable of doing so.
Whoever wants to implement it in Rust is very much invited to apply for funding at whichever council
=> See here the beginning of the RFC, lets make this an awesome Community RFC 