Part of me says do it right, propose an MBG and teleworker devices and reiterate to them that this is the CORRECT way to do it... if they really NEED it badly enough, they will get the process fast-tracked or find an acceptable alternative which may or may not be temporary. It is not uncommon for us to bring in a completely separate internet connection just for voice, plug that into WAN, connect LAN to voice VLAN port, and you're done.
Doing stuff half-assed often leads to more problems then it's worth, then again, the other part of me says do whatever you can to make it work to help the customer.