The comprehensiveness expected of current RFCs is a high barrier to entry and as a result there are relatively few RFCs proposed each month. "Proposal issues" will be much easier to write and I expect they will be opened at a comparatively much higher rate, and probably rehashing old questions (eg. https://github.com/rust-lang/rfcs/issues/2831)
If the goal is for these issues to be periodically reviewed and individually discussed during meetings, they will need careful management and prioritisation to avoid overwhelming the lang team.
How do you see this prioritisation happening? It sounds like there may need to be a strict policy of closing issues to ensure the number of open issues is kept small, but it will be difficult for such a process to be fair and transparent.