Well, after a couple of afternoons pottering around (yay, school holidays!), I've just dropped off my Steam Powered Zappy Gun for Andy to flock for me (kind chap that he is). So, just before I popped out...
It's worked out really well. One thing I would like to change is the way I've connected the cables to the generator. Basically, I chopped them too short. Works well as is, but upon further reflection it would have looked even better had I left the wires long and had glued them coiled on the base. Ah well.
Oh, and I deliberately left the braiding on the officer black (undercoat as it happens), as per this...
...and this very helpful page here.
And so, I can class it as a General's element - either Magician or Artillery for HOTT - or just plain a Contraption in G.A.S.L.I.G.H.T. If I ever get round to actually playing a game now I have the rules.