As far as I am aware, there is no way to filter for specific forms with the /randbats command. While this isn't an issue for 99% of pokemon, if you have something like Arceus, with 18 forms and 20+ sets, it can be a bit of an issue to have to sift through all sets to find the one you might be looking for. This is ultimately purely a quality of life feature that is entirely unnecessary, but I figured I'd make the suggestion anyways in case someone felt compelled to try and add this suggestion.