All right I went a bit overboard with the rockets. I should have suggested Mamoru to wield one. The thing is that when I read about damage values for armed combat in the Sailor Moon Rpg book, It explicitly stated heavy machine guns and explosives, which is apparently Wiseman's big weakness!
And let us not forget about Usagi /w chaingun in the Mamoru is useless topic
On-topic: Guns would be interesting, but mainly by allowing the non-sailor cast to shine and do something other than fall victim of the current villain's machinations, allowing the plot to take different turns, and the conflict to escalate beyond Tokyo even with the main heroes stationed there.