https://phabricator.wikimedia.org/T30856#3314789 needs investigation
Topic on Talk:Contributors/Projects/Removal of the 2006 wikitext editor
We just want to keep the blue buttons and the ability to personalize them, that's all.
The very few buttons in the Vector toolbar are useful for newbies but a bit limited for experienced users.
I assume there wouldn't be a problem if the old toolbar can come back with an extension or gadget, available in all WMF wikis that each user can enable on its own.
The linked task and this project page doesn't make it clear if the current old toolbar will still be available or every user that wants it would need to hack it on their own...
Any editor should feel free to re-implement the code as a user script/gadget.
From phab:T30856#3325233, the French Wikipedia may have already done so.