Backoffice theme

[Inform-All]

I might be (i hope i am) completely wrong, but is there currently no 'good' way to edit some parts of the backoffice theme?

I'm not talking about the core admin theme parts because those extendable (docs).
Because the docs also say that you should not override, and can not even override with a custom module, i don't see any other methods...

So what would be a good way to edit let's say ANY block inside of /adminXXX/themes/default/template/page_header_toolbart.tpl ? 

[fbenoist.com]

I'm sorry, but I don't think there's a good way.

[tapanda.gr]

If I were you I would do it either modifying the admin theme or copying, modifying the renamed directory and then enable it in the settings.