Could you combine copilot with an updated linter or similar? In Visual Studio the intellisense does a pretty good job of converting my manually-typed old way of doing things code into a newer, simpler version supported by newer releases of C#.

Example:

    using (var reader = new StringReader(manyLines))
    {
        string? item;
        do {
            item = reader.ReadLine();
            Console.WriteLine(item);
        } while(item != null);
    }

becomes:

    using var reader = new StringReader(manyLines);
    string? item;
    do {
        item = reader.ReadLine();
        Console.WriteLine(item);
    } while(item != null);