This general idea is exactly why I love nix. The immutability of it is powerful. It can be useful for both running your agents in a certain environment AND your agents are useful at writing your nix config. I expand on this in a blog post here https://jamesst.one/posts/agents-nix
I have a tangentially related problem I have been battling with that you may be able to help me with. I'm moving overseas (Australia to Denmark) and would like to keep my current mobile phone number working for calls and SMS , but use it from afar. I would be able to leave a raspberry pi at a friend's house. Can you use this setup without a SIP provider? Would you need to buy a modem for the raspberry pi?what would you do?