The issue that's solved is that it bins off C&O and a separate official having to make judgements and returns us to "what does the referee think is the correct decision?" I'm baffled that you seem to be minimising how clear a benefit that would be.
The rest of the concerns are valid, but not prohibitive. They might be issues, but they're also not beyond any possibility that they might be solved.
I'd rather have a "ref, challenge X" conflict over a "ref what the f*** are you seeing, are you f***ing blind" that seems to be common in the PL currently.
Determining what is being challenged involves.....talking to people, doesn't seem that hard?
Who shows what is an issue under the current system, so nothing new there.
And the other assorted questions are just that - questions, not impossible obstacles. Again, they need to be addressed, but that's it.