What we need to remember is what W10M really is: OneCore on ARM. The same as Windows IoT. What was Windows RT.
Everything it does is just Windows. Phone calls and SMS are just a cell modem...
Couldn't you use RemoteApp (which XP Mode used a hack of) from the Client Hyper-V machine to get the same effect on 8?
Another option is that a 3rd Party developer will create apps that are compatible with CardDAV and CalDAV so yours can sync their stuff
Actually, MS does have a cheaper plan: the $4 a month exchange only plan that I'm using