When uploading someone else's firmware from another device, there is a very high probability that one of the pins, which was configured as an input by the native firmware, will be configured as an output by someone else's firmware. And it turns out that, for example, the processor output will be connected to the FPGA output. And if the processor sets it to 0, and the FPGA sets it to 1 (or vice versa), then there will actually be a short circuit on both of these outputs. Will both of these outputs survive, or will the output driver of one of them go into oblivion - a very interesting question. I wouldn't want to learn the answer to this from practice on my several hundred dollar oscilloscope.
Thats possible, but IMHO its higher chance of hardware damage caused by ESD - from my personal experience. Anyway, If I will fail, then I will have story to tell. Speaking of reverse engineering, in libscope-auklet.so there is a banch of decoding (audio, aviation buses, power calculations) options which so far currently nobody unlocked - looks like its for other models in vendor.bin and it can be disabled by hardcode. Its not easy to read dissassembled/decompiled code, but I think thats possible.
I assume that Rigol chose to transfer the data to the RAM as 16bit numbers (and not 12 bit "interleaved" since the overhead would be excessive) which results at a sustained transfer rate of 20Gbit/s @ 1.25GSa/s, add some small overhead and the 25Gbit/s specified for the ZYNQ doesn't seem too generous...
Even though it's a pity, I highly doubt that an up-hack of the DHO800/900's sampling rate is possible with the existing hardware. I'ld be glad to be proven wrong...
So theoretically if data going from ADC to FPGA is without any checksums or other overhead, then without overclocking or changing FPGA it should be possible to do 1.25 * (25 / 20) = 1.5625 GHz. That exact number probably would by tricky in changing mentioned lib, because they made sample rate ratio with multiples of 400, 500 and... 625. I just started to decompile this .so, so there is a lot more things to read and test it...
I did the "impossible" things before. Sadly I cant tell of most "impossible" thing I done, because its a secret - somebody payed me just for trying and I succeed anyway and that took months of hard work (half of it was caused by my stupid mistake in a code...).