I don’t really like this idea. I think an equal value to being a database for observations that can be used in scientific research is teaching people about wildlife and getting them interested in it. So I think the pros of iNaturalist’s open approach outweigh the cons. (Besides, most IDs I get still are by people who seem to know what they are doing)
Personally, I have learned a lot by way of IDing that I likely wouldn’t have learned if there was an extra hurdle to becoming an identifier. I have made mistakes, of course, and I still make them. As I am constantly monitoring my inbox though, I tend to catch my mistakes rather quickly, and judging by the behaviour of most other IDers, the vast majority of them does as well.
This may be a good compromise. I do like to check the CV to learn about similar species I was previously unaware of, though, so I don’t know if I would use that feature.
It could be an interesting experiment to display the identification accuracy on a user’s profile (though I am not sure it would be a good thing to add in practice). It might also change the “gamification” aspect previously mentioned in this thread into one where quality counts just as much as quantity because it’s not just about seeing the absolute number go up.