I have not read this entire thread completely, but why are you needing sustained data rate? Usually, when acquiring a signal, one builds up the signal into memory and slowly transfers the data to the processing unit. This lowers your repetition rate, but you can easily capture higher frequency waveforms. Sustained data rate is not common and is usually only used in very advanced areas. Theoretically, you should be independent of the communication rate and the communication rate should only come into play when you need a higher rep rate.