Leon,
18kbps for each buoy (x32-ish) is I agree not a big ask, but how much bandwidth would be required for the EO/IR and the radar, plus all the command data? There is only a limited amount of bandwidth available to support UK military operations, unless we start buying it in the commercial market, not known as a cheap option. Of course if your solution is to provide BLOS bandwidth with a dedicated satellite, how does that effect the cost/benefit comparison with a manned platform.?
I feel that you are trying to force a square, though admittedly rounding, peg into a round hole. Give it another 10-15 years and cheaper bandwidth then I think it might work.