1. Without forging fees, how will you combat spam? I have only talked to one developer that has said he can do this and his coin hasn't been released so there you go.
2. The approach of putting it all on vendors and their hardware is in theory a sustainable model, and one I think is a good idea, just not from Crypti. The problem is the bootstrap. It would literally take a company like Apple or Google to release their iBits or Gbits to get mass amounts of retailers to update their hardware.
Crypti doesn't have the money, power, or pull of Google or Apple, so trying to get vendors to install new hardware is a dream. Your best bet would be to find some pre-existing hardware that would be compatible with Crypti and try to get a firmware update. It couldn't be a hack because nobody is going to trust a third party changing the code in their POS terminal. That is unwise. Sooooo, that means talking directly to the manufacturer and good luck with that. I'm not sure if you could even get somebody high up to even answer the phone.
3. As Starik pointed out, then this system isn't decentralized which of course is not necessary, but it is, because it is an established cannon rule that whatever crypto win the alt wars be, it must be decentralized and open sourced.
4. There is some great theoretically ideas being tossed around here about how to solve many of the PoW problems that Bitcoin has plagued us with, but the answer just hasn't come yet.