I'd be excited for new tools but as others have mentioned it could cause a lot of balancing headaches.
What if something simpler and more elegant was introduced, like... Only Gunners are able to buff guns? All classes can still use the tool, but Gunners can only buff guns with it and Engineers only non-gun parts (balloon, hull, engines).
Of course, that means the gunner would be unable to repair as his one tool slot is taken up by the buff tool. It does introduce a new set of interesting decisions, however: Do I stick with three engineers so all my men are able to repair, or do I want to have access to the higher dps that other ships with 2 engineers and 1 gunner will be packing?
Gungineers would be upset, yes, but nothing's stopping them from continuing to gungineer - being able to shoot a gun with a complimentary ammo type while having the ability to repair, put out fires and buff non-gun parts keeps them being overwhelmingly useful without having it all.