You're going to have to put a single router in front of those wireless connections.

To do it properly with bonding of uplink and downlink, you're going to need the router on your end configured to do it and support from the ISP at the other end.

If you are happy to lock each client machines to a specific wireless interface then you don't need the ISP support. You'll want to force each machine to only use one wireless interface because you don't want connections from a single client coming from multiple public IPs.

Can you get line of sight to somewhere which can get a proper internet connection? I've no idea how much the permits and equipment necessary to do a point to point link for your situation would be though. I'd be guessing more than the 10K that has already been invested into this...