The reason, why there isn't such a keyword is that a) there is a lot of stuff that must be written to disk. If this would not be possible, ricc2 could only stop, and b) with all the functionalities implemented in ricc2 it is for this method rather complicated to keep track of the disk space that has been used.
So there are only these 3 work arounds:
a) use a machine with larger disc space
b) run the calculation MPI parallel so that the files will be distributed over the discs of more than 1 machine
c) use the LT-SOS versions, they need less disc space if you just compute excitation energies, but for many states
Christof