First of all: thank you for all your comments and efforts ! I really appreciate all of them ! When I see all this, I take confidence in the human being... You have all my respect.
Seems that we may have a potential solution (?) :-)
I know that we can't close all doors... it is perhaps not prevent all risks, but to learn how to manage the limit (can we say that in english ???)
I downloaded IntraACL from the "storage-rewrite" git branch to do a test. Under patches/ there is no IntraACL-MediaWiki-*.diff for our Mediawiki version: 1.21.1 Anyway, I have done a backup of our dev virtual machine and then try to to apply IntraACL-MediaWiki-1.20.3.diff to our 1.21.1 installation (just to try and guess): of course I got some errors on lines xxxx...
Question: is there a IntraACL-MediaWiki-xxx.diff for 1.21.1 somewhere ? Else, do you suggest to install 1.20.3 (or 1.20.6) instead of the latest MV version ? (because there is an available diff for 1.20.3...)
Again: thanks you all !!!!
I'm sure storage-rewrite still has bugs, so I think you should better take master by now. Rewritten version will be totally compatible with current one (the update will be as easy as just running maintenance/update.php).
I've updated the patch for 1.21.1 - it's not so hard, but I didn't test the result yet :-)) you can pull from master and try it out :)