Thank you for your answer!
Hardware has external reference input which (at least in theory) can be used as common clock reference for two RX which also exist in FDM DUO hardware.
You are right, USB is not synchronous interface but we can overcome its disadvantages. There always will be random delays but we can fight these in the software with the use of cross-correlation by receiving known signals by two receivers.
So theoretically it is possible. But I would like to know if there is any progress in this direction if possible. Or are there any hardware constrains in ELAD which make this impossible dream?
Thank you for your thoughts\ideas!