Idiomatic presumes there is some gold standard of style you can use with C++. Dude, there is no such thing as "idiomatic C++". I've seen lots of idiotic C++, sure, but idiomatic... every team must select the subset and style they use by themselves. With expert users some specific patterns start to emerge that they've found lead to least horrible code.
What makes you think that this "modernization" will make it more maintainable, leave alone more idiomatic?
Generated code is unlikely to be more maintainable.
Code is code. I doubt a computer program could do worse than my undergrads, indeed it will probably be functionally correct. Today I fixed a bug where a condition std::thread member used a condition variable in the constructor, problem was that the std::thread came before the condition variable in the structure declaration. No computer would make that mistake.