Agree completely, I will also eat my shoes if this gets put into action.
Here's how this could be playing out in actual fact.
1. Supermarkets are largely honouring the price controls (although "creative shelving" seems to be their way to minimize impacts). Shortages, etc. for now aren't a big issue, but the margins are being erroded by inflation. Supermarkets are making less profit on items, but still being charged same % by banks for credit cards - they want some relief as a 1-2% reduction could erase the losses from inflation via price controls.
2. Moreno, either strategically to send a signal, or hamfistedly after floating a crazy idea in a pre-briefing to the meeting, suggest the MorenoCard idea. Supermarkets are at least somewhat amenable if they get their rate cut.
3. Gets media coverage, and supermarkets temper their public response. Banks and chinos freak out for obvious and justifiable reasons. The impact on daily life could be tremendously negative, and make things a lot worse.
4. Banks don't want to see all that revenue from credit card use in supermarkets evaporate, so they get together with the supermarkets and offer to cut the rate to, say, 1.5% for business subject to price controls. A bit higher than the government, but no cost to implement, change technology, angry customers being alienated, etc.
5. Banks and supermarkets announce agreement and supermarkets push Moreno off the idea (he'll probably have a new crazy one by then anyway), which probably would have taken an enormous amount of political capital and time to get off the ground (inc. legislation) at a time when CFK & co have precious little on hand with more nationwide marches being scheduled ala 21N that might bridge middle and working class for the first time.