I think the proposal sounds fairly reasonable, but it is hard to say how well it will work in practice until we try it, and we should be ready to change it if needs be.
Some clarifying questions on the intended process:
1. After submitting the initial merge request, is the person making the proposal to wait for any kind of acknowledgment, or just move on to step 2?
2. Is the discussion going to happen on one of the mailing lists, if so which? Is it the job of the proposing person to involve/notify the committee about the discussion? If so, how are they to find out who is on the committee?
3. How does one actually perform step 3, another pull request or simply an e-mail to someone?
Typo: two separate bullets in the proposal are labelled as 4.
Cheers,
-Iavor