Sticking with Cisco gear will get you higher power radios and with an external antenna model you could get some directional antennas with a much higher gain and either place a router near or in the elevator shaft (if possible) then have an AP in the basement near or close to the elevator. I would mount the antennas in the elevator shaft (also if possible, to get around the elevator with any luck) with some LMR-400 or similar low loss cable routed back to the radios.
Otherwise you could place the antennas out the window with the router pointing down and the AP pointing up (directional antennas that is).
Without knowing the exact layout of the building and the situation its hard to say for sure, you may need to throw a second AP in the middle somewhere.