You actually don't need location permissions on in GMS for Google Maps. Maps has its own permission request. Although you're correct that GMS needs sensors for the compass functionality to work in Maps. The recommended setup is to keep location off in GMS and use the OS rerouting feature.
I don't see why GMS would need nearby devices; I bet you could kill that.
If you want to use Google Wallet (not for NFC but just to hold things like boarding passes and tickets), GMS needs the Phone permission.