It doesn't scale as you need to share the number across different services. To be completely decoupled you'd need to have 1 number per account all bundled into one sim card. I don't think this is something you can setup with current services and phone software.
I mean, you could do it with Flowroute or Twilio. I already pay $1.25/mo for a DID for my home from Flowroute, if I cared enough about security buying another isn't going to put a dent in my pocketbook and I could just have a small little flask app somewhere forward them to a prepaid phone.
