Wow, Glenn the idea of an on deck (IXC) torpedo moving diorama sounds more and more interesting the more that I think of it.
Here are a few thoughts on it.
1st Deck line and up display. Use just part (1/2?) of a IXC deck. Left over (?) from a deck upgrade?
2nd Use railroad rail for the tracks to roll on. HO scale 1/87, this is 1/72, but it's close.
3rd Turn some wheels (4) on the lathe add axles and other stuff for the trolley.
4th Us 1/16 brass tubing for the poles. Need to make wench and other small items.
5th Use a cmk kit or ? ramp set up to show a torpedo going into and down the front hatch. (cut torpedo in half, cut at angle)
6th Use 2 torpedoes?, 1 on trolley and 1 going down the hatch. Or just use 1 - to show off trolley without a torpedo on it.
Of course as I sit here at a desk typing this I look down at the Trumpeter 1/48 scale sub and say why not up-size it. Do 1/48 scale?
Group Build thoughts also come to my mind.
Later Tim