"Also ideally needs a parameter to force cleanup of literally-stored utf8 data in non-utf8 tables (does binary charset change)." Since Composr now enforces the right communication character set, encoding problems are not buried but result in visible errors. Corruption cannot creep up, so this is not needed.

I'd consider this functionality quite critical, except that most users will create their databases as utf-8 in the first place if they are using a non-anglicised host. That is fine, the default Western European used in Composr's EN pack works great with a utf-8 DB now.
Plus people can do an export then re-import into a new DB, if they need to switch the DBs charset.

So it's not an awful situation. I'd still love this Commandr command to exist. Probably next time I need to do a conversion I'll write the command and use it.

As Composr is moving to utf-8, this will become irrelevant.