If you want to change Rorqs in a way that isn’t a nerf, but still take away their mining power, I don’t think adding compression is going to do it. (They already had that anyway, right?)
But think how cool it would be if you gave them refining! That could make the skill point investment feel worth it. A little, anyway. Depending on how efficiently the Rorq refines.
People are already accustomed to expect refining in a station will bring losses. Whereas giving in-station compression a new loss factor feels nerf ful. So if the Rorq had better refining than an NPC station (maybe still equal or worse than PC stations.)
Then there you go: now it has been buffed. And people still won’t use them to solo mine.