I think a few different concepts are being muddled here.
Flagged revisions (and its variant, pending changes, on enwiki) is applied to individual articles to hold *all* edits from certain user classes for review.
What Petr is looking for is a way to flag *individual edits* to an article (not the whole article) for review.
Flagging edits for review through either method means creating an expectation that someone else will review the edit. The use of FR/PC is (to date) only enabled following community discussion and usually community determination of the applicable rules for its use. I suspect that enabling a means to flag individual edits would also require some sort of community consensus for its desirability before it is enabled; however, someone's going to have to write the code first before that happens.
This does come back to basic socialization of the editing/reviewing process, and likely some (project specific) rules of thumb for when to revert and when to take a few minutes and research the new data would be worthwhile. For example, I'd probably not revert the result of a sporting match held within the past 48 hours, but I'd probably revert the same edit if the sporting match was six years ago. Dates of birth are particularly sensitive and changes to them should always either be sourced or the prior consensus verified. It's often better to review fewer changes and verify information (most of which is usually available somewhere online) than to get as many edit reviews as possible done. I can't tell you how many times I used to get edit-conflicted by people using review tools when I used to manually review (and fix) recent changes.
Risker/Anne