I would allow the assist:
R2 helps Luke all the time. Increase power ...helps with repairing the shields...etc. This could easily be translated to a boost dice for piloting checks.
I would allow the piloting:
to an extent. Simple flying, autopilot or simple plotted course: translated to-- basically warning PCs if autopilot messes up or something is wrong in the plotted course. Anything else is for PCs.
That's the entire point of the astromech socket in X-wings, though. R2 couldn't turn off the tractor beam in the Death Star, or reverse its engines, etc. He could only access what was available on the network he was slicing and it makes sense to keep those kinds of system isolated with no way to backdoor through slicing.