There's room for building instruments like this at a state-sponsored level in, say, the EU. The EU has already been working on a special clearing house that would help European businesses circumvent the US-imposed sanctions.
You are not wrong on facts. The problem for Iran is that EU does not really seem to want to actually do anything other than words and vague promises. Instex was a promise of sorts, but UE chickened out ( for a good reason after most govn. representatives including Lindsay said something along the lines u either wiff us or against us ). One of the reasons Iran grabbed a ship was to pressure EU to make it an actual option and not a talking point.