Any sort of plastic or sheet metel would void the warranty.
I know this isn't completely true because you can buy plastics for transparency printing on inkjets at any business supply store, and they're made by HP, Epson, etc. The plastics I have in mind to print on are artist's acetate, which are not very different and well under the 48mil thickness max of my printer. But what I need to know is what the characteristics of the surface have to be to accept the ink well.
I am fairly certain your printing heads would be at serious risk!
Based on what? You may be right but I want to base that on specific knowledge not emotional fears. By way of comparison, I've had conversations about darkroom chemical safety with laymen who were concerned about having a darkroom in their house or apartment. Now it's true that some darkroom chemicals are dangerous - some are caustic, some can cause cancer if ingested, etc. But the laymen invariably focussed on the risk of fire hazard and explosion, which are NOT significant hazards for the chemicals I use. So my point is that by understanding these things we can assess risks rationally.
As for cloth, there would be an enormous jamming potential with the rollers.
Plenty of companies sell canvas and linen with special coatings for inkjet printers, and these are almost all less than the maximum thickness the 2200 accepts, so again, I don't think what you say is entirely true. There may be "some" jamming risk but "enormous"?. Keep in mind that the manual-feed on the 2200 is a straight-line path - this is not a Xerox machine or laser printer with a convoluted paper path.
Inks and dyes require a mating surface - which is paramont to their success. Years are spent developing suitable papers. As an illustration, try printing on the BACK of an Ilford Smooth Pearl paper and notice the runny mess you get! This sort of experimentation is very costly in time, materials, and equipment. You are operating beyound the design parameters of your equipment!!!
That's not at all clear. As I already said, I've gotten good results printing on gesso'ed canvas and brown paper bags. Furthermore, "giclee" printers have been inkjet printing on novel materials for 10 years now.
Sort of like taking underwater pictures with a Nikon N90s - and no housing. I don't mean to sound like a smart ass, but the question is almost unanswerable.
Sorry, but that IS a smart ass answer. There are plenty of 3rd parties that make paper and other media for inkjet printing so this can't be some sort of deep dark trade secret. Plenty of photographers develop outside the bounds of their darkroom chemicals, print through water or other media, apply emulsions to non-standard surfaces, use weird things for filters, hand-color or paint prints, use their own tinting chemistry, et cetera, et cetera. No one says THEY are doing the equivalent of underwater photography with an un-housed N90. But in order for them to be successful they need some knowledge of the underlying properties of developers, emulsion, etc.