There are a lot of different throwables in the game that might fit "Engineer" but I think some of the ones currently in it like Holy Water and Acid Flasks don't quite fit what an engineer would be making. Maybe take them out and add some different ones that have a more "engineer" feel to them? At the very least maybe just remove Holy Water from the list....as it is pretty much impossible to contrive a way an Engineer would be tinkering together some water blessed by a priest to fight undead <_<