Agreed – semi. Found them both, scope and lock-in, very useful in physics experiments, lock-in always in somewhat special photoacoustics setups and scope, yes, mostly in a rather generic use. Still it does not impair the feasibility of lock-in amplifier instrument implementation on RedPitaya.
I am speaking of reference generation, (most probably) digital PLL and DSP alowing for in and out-of-phase component sampling – i.e. two phase lock-in.
Handling of I's and Q's was shown already (script) – even though offline and for a different purpose. That is right – for lock-in the implementation on FPGA is a must in order to realize longer sampling. Resources are enough on red pitaya's Zynq 7010 to do it. As said, it's feasible, it is all just a matter of efforts... as always 