I do indeed like the canister being angled.
As far as it's purpose, I always thought, at least for the XGB packs, that the packs minus the canisters were basically the same power level as the classic GB packs. Rather than re-craft the entire accelerator or internal system of the packs to give a greater output, Egon designed the canisters, which house the extra boost that the equipment needed against the "new breed" of ghosts. Sort of like the stuff you get at the store you use on your yard. Sure, you can water your yard and it may or may not help, but if you buy the stuff, connect your hose to that, and spray your yard, it should help out more.
Or something like that anyway. I don't know what the yard stuff is called, but I hope someone knows what I'm talking about
I saw your classic thrower + cannister idea Charlie and it gave me an idea of my own. I can draw it up if you'd like to see it.
And I agree with the others irricanian, that un-finished custom pack is cool. Definitely deserves to be finished.