Hi Jerry,
Regarding your question as to how I could afford an air-wing on a 1/350 carrier with the models at $17, the answer is that I can’t. 
The fact is that 3D printing is still fairly expensive, and likely will be for some time to come. I haven’t even bought all of the planes I’ve made yet. Sorry, but there is nothing I can do about that.
As for setting it up so that people can pick and choose the parts they like, it is a good idea, and C2D once told me that they were considering doing something like that in the future possibly, but currently they are not set up for that, and I don’t know when that could be, if ever.
As for just purchasing certain items, I think that could be arranged. C2D does custom orders too. If you let me know what you want, and how many of them I can let them know and have them give you an estimate of what it would cost.
AS for the conex cans, I think I have already made some that would work as you can see in the image below of the 1/350 scale USCG Cutter Bertholf I was working on for Admiralty Model Works. Same thing, let me know how many you need and I’ll contact C2D.
With respect to the tilly crane and other deck vehicles, I have already made a set for Admiralty Model Works, who has them available on their web site at:
http://www.admiraltymodelworks.com/admiral/component/virtuemart/1-350th-accessories/usn-wwii-deck-vehicles-detail.html?Itemid=0
If you want to contact me directly, my e-mail is rdutnell@ou.edu.
CHEERS!!!