Not dead; still dying

Instead of having the FPGA in the external device, one could replace it with a microcontroller that stuffs the data into packets to be sent raw over Gigabit Ethernet. On the other side of the intertube then exists whatever solution one decides is appropriate to handle the massive flow of data, such as one of these:
http://www.picocomputing.com/

This should have the added benefit of decreasing the noise present at the ADC, and decreasing the power requirements. With Power over Ethernet, the device could be very simple. And cheap.

The ADC should probably do no more than a little over 60 million samples per second at 12 bits per sample, and be strongly capable of undersampling.
Between the ADC and the analogue signal source must exist an amplifier, bandpass filter, and possibly a dynamic range compressor or limiter to deal with strong signals. A modular design should allow for cost saving. These are all traditional radio design issues, so an elegant solution should already exist.