Lining the exterior walls doesn't sound all that hard for a new build. Just lay the RF blocking sheet down before the drywall. People love those RF blocking wallets that have dubious value, a "privacy wall" upgrade from builders would probably sell well.
They can sell it as improving Wi-Fi in your own home too, even if you trust neighbors not to pull any shenanigans, since your Wi-Fi network won't be subject to interference from neighboring networks.
That's an inconvenience for guests but you could stick a QR code to join your wifi on the wall. Phone calls should still work over wifi calling I'd think.
Just put a mini cell tower/booster on the inside of your house connected via wire to the outside. Problem solved, and you now have the ability to cut off cell access on the inside if you want to.
