There was a company who was selling IP to do this sort of thing in FPGAs -- using an LVDS input pair to drive a soft core implemented in programmable digital fabric to implement an analog to digital converter. One of the advantages they talked about was using such a part in space -- if you already had a space-qualified digital FPGA -- it was quicker / cheaper / less risky to implement an ADC in the FPGA's digital fabric than to space-qualify an analog part.
I believe it is Stellamar -- they sell other IP and used to be in Chicago. Xilinx, Actel, and others offer their IP via a third party arrangement. There also are ADC in FPGA app-notes by Lattice, and Altera.