I understand what you are aiming for, but I wonder if extra time would actually help. I have the impression that if an RFC doesn’t “catch fire” and generate a discussion as soon as it is announced, it then tends to go completely unnoticed (until voting starts and then the proposer is surprised by people raising issues that were not mentioned during RFC). Having more “live” RFCs competing for attention at any one time might make this even worse.
I agree that it might be useful to make a bigger distinction between proposals that imply deprecation versus those that simply introduce a new tag that does not conflict with anything else. But I’m not sure if “more time” is an effective distinction to make.