Is it possible to have an "accreditation" process
Yes, definitely. It is possible to measure the load on a new TLD with medium interest, and to test whether a proposer of a new TLD can meet that load.

that also has an element of checking for harm to others (and what harm would be relevant)?
No, definitely not, as the folks above have shown. To throw in a much more sensitive problem: .canada, .france, .españa, and so on.