Concrete walls separate the rooms, and the one long room is a semi-corrosive wash-down area. Staff use mobile devices that require a strong, uninterrupted WiFi connection, and they are often moving throughout the building while using the devices. I don't want repeaters or extenders or any other mechanism that would result in multiple SSID or channel connections for a tablet to contend with (dropouts for reconnection, or failure to switch to a stronger signal, etc). I just want to use one access point, but just with better coverage.
Instead of trying to buy the most powerful access point on the planet, using brute force to blast through those walls, I was thinking of using extension antennas. So I'd take a consumer-grade access point with 3 standard antennas, remove 2 of them and replace with coax extension cable (green in the image) and keep 1 original antenna (blue).
Especially for the wash-down room, I was envisioning drilling a hole in the concrete wall and slipping the antenna cable through, so in the end, only an antenna would be exposed to the corrosive environment, and still provide good signal strength to staff in that room.
My ultimate question is: will this work? Is there something I'm not aware of, like perhaps that access points with multiple antennas aren't designed to work with their antennas separated by 10-20 ft?