I'm not very concerned about the two channel system, it is what it is.
Always look at the long term cost of each option. The existing equipment is aging and at some point you will be faced with repair or replace. Even now, you'll probably be pulling wire for those Volume controls. Balance the cost of pulling wire, along with potential service/replace options in the near term for the current equipment reuse vs replacing things now with equipment that will not need in-wall controls and the repair/replace clock is reset.
Measuring voice coil resistance is not a substitute for knowing the speakers impedance. Check with the manufacturer. Also, Bose speakers assume that they will be driven by a Bose amplifier that has been equalized for use with a that model of speaker.
Regardless, step back an decide if the resulting user interface will be appropriate with the customer's current expectations.
Ten years is ancient history. Ideas that were enormously impractical and/or super expensive then are now a cheap trick. Systems that we put in a couple years ago are now stale, we will never do things that way going forward. Systems that we are about to install are already obsolete. I'm already planning for next year's models (not yet available) and many of today's go to models are not on that list.
It's a network world. If the walls are open or not yet painted, run plenty of network wire and make sure that WiFi coverage will be adequate. Also keep in mind that wire is running out of bandwidth. While it might be "dark" in the immediate future, in a few years you'll wish that you had pulled some fiber.
