Computing and storing local matrices

I missed to bring this up in our meeting yesterday @kohl @mohr. There was a discussion on having computeAndStoreLocalElementMatrices like the old operators which would be useful to speed up simple isoviscous runs and even in varying viscosity runs (in coupling picard iterations for e.g.)

Is there some roadblock to implement this in the new operators or just that it wasn't on high priority (which ofcourse I understand)

I could try to implement this at some point if it will be possible.