Proxy server (e.g. Kamailio) in the cloud to share trunks, good or bad idea?

I have one office with a Freepbx server in California, and one in New York. What do you think about running a Kamailio server (or another proxy server) in the cloud somewhere between east and west coast and use it to register my voice service provider’s trunks to, with each Freepbx box in the two offices connecting to the Kamailio server? My two offices would then be sharing trunks to the PSTN and therefore save money.
Good or bad idea and are there better alternatives?

Does anybody have recommendations?

A good idea, IWFM, I would put up a cluster of two ,( one on each coast) for robustness,