The problem with that is someone is going to have to pay for it, do you want to pay the full cost? The cartridge makers make cartridges and it would be almost impossible for the to do the research and development on cases and wad materials them selves they would have to go out to other companies to see if the make a product that could be adapted to be use for cartridges and it all takes time.
What is worse for the environment plastic or lead? I've tried both standard and hp steel, nether seemed to carry the energy of similarly loaded lead (in a very non scientific test). The hp steel wasn't too bad and had I tried different brands loads etc I would have probably found something as good as the lead but there steel isn't that easy to find around here at the moment. plus only one of my guns is steel proofed and most of the places I shoot have ask that I don't use plastic wads.
I agree with the idea of getting rid of plastic and some lead (I wouldn't be happy using steel for humane dispatch! not looked at bismuth etc) and would be happy to try anything but I think it would have been better to try to get manufacture's and shooters on side first.