Rocket launchers seem unlikely, unless a real war happens. For general security, they're really not necassary, and the resulting large blood splat and the floor scuffing...honestly! What are those slaves beaten for?
Swimming Sligs seem unlikely. No water threat has really been seen at all, Gabbits were believed extinct, and a single one would probably not be considered a threat as to create a whole new system to try to destroy it. Wait for it to come up on land, where it's actually a threat.
The mechanics for flying Sligs in 3D may have been difficult to program. Sorting bugs for that sort of thing shouldn't have been the same problem. Or, perhaps, a limit to height, just so you can't go over the map edges or anything ridiculous, like the Banshee's limit in Halo (I love those things
) or similar.
...Sniper Sligs? With scope masks, for hired asassination purposes by Glukkons, and protection during large conferences, perhaps, to target possible threats.