Y'know, there is some relevance in a significantly asynchronous circuit with this stuff.
I think the correct label is "asymmetric" but many people call it "asynchronous"...
Put the High speed TX on the top of the mountain and have it push high speed frames in broadcast or multicast mode whilst the outlying stations listen to the stream and write down the packets relevant to them.
This is of course what I had in mind. We don't have any mountains here but we have a 3cm ATV repeater at 220m in a broadcast tower transmitting a DVB multiplex where we could use some bandwidth (or e.g. the bandwidth remaining after the several variable-rate encoded ATV channels have had their share) to transmit IP over DVB. Both broadcast/multicast traffic (like IPTV streams from the repeater) and traffic to a single endpoint (after all, we do not hide traffic from eachother). The return channel could be much slower indeed, depending on the kind of traffic and the required return traffic. Maybe even a 9600+ baud packet link, or one of those newly developed 70cm links of about 400kHz width. At the moment the repeater is not operating, but we are working on getting it back on the air.
Rob