I currently carry a dual-sim phone to have two numbers, private and work each. I am not entirely happy with this setup however:

• Dual sim phones aren't common and cost more when I have to upgrade.
• I need call recording for business, but android phones aren't very clear when it comes to call recording support. I had to try and return several new devices.
• I would love to have additional temporary phone numbers for privacy (e.g. retails).

And here's my situation:

• Google Voice is not available in my country. Plus, it's Google.
• Prepaid SIM cards are cheap and easy to acquire where I live.
• I have a bunch of old spare android phones.

I was thinking, could I leave the SIM cards for private and work at home, inserted to phones/devices that are managed by a call-forwarding server, which transparently forward the calls to a third device I am actually carrying?

Self hosted Google Voice is what I would love to have.