> But then you are reliant on a different carrier and network for yours to work.
Why? You could easily enforce a policy that only who use your fiber network at home qualify for these femtocells. Considering that majority of backbone fiber is an oligopoly already, this wouldn't be an issue.
> Most users home routers are garbage for latency and loss sensitive applications, of which voice would qualify.
Do you have any source on this claim? IP network has become just as fast and resiliant as the pure teleco network (reason why 5G is based on IP in the first place). IP calls from Facetime, Google Duo, Skype, Zoom, Whatsapp and others work just as good as regular calls if you have decent coverage. And you can easily implement QoS for calls through your own network, which is what the old 3G/4G tech was already doing.
> And that easily opens up the network to cell site spoofing moreso than they already are
How common is WiFi spoofing in your experience?
> A big reason LTE, GSM, evdo etc were successfull was because the full stack, from the backbone to endpoint/user was managed by the carrier
The reason they had to do that was because IP stack wasn't good enough 2 decades or even a decade ago. Unless you are in a 3rd world country, IP network is just as good as 3G/4G stack today.
> Offloading that to home users who actively put routers in between interference sources like windows, fridges, washers/dryers and then tey and extend their signal with repeaters is a questionable goal at best.
Okay, you might want to revisit that thought couple of years from now :)