As for part 2, I would be recommending against it since MW isn't only used by WMF wikis, So we should be keeping the defaults nice and clean for the other communities that may be wishing to use it and only things that are required and try to choose names that minimise the impact/chance of duplicates.

(In reply to comment #0)

2.) Suggestion to add:
add additional entry in interwiki.sql
'bugzilla','http://bugzilla.wikimedia.org/$1',1),

Not going to do this per comment #1.

3.) beautification of interwikis in enwiki, dewiki (and probaly others):

That's a request to make on Meta, not here.

1.) suggesting a patch in interwiki.sql because the bugzilla url has changed
and http://bugzilla.wikipedia.org/<bugnumber> is not working any longer:

change

'mediazilla','http://bugzilla.wikipedia.org/$1',1),

> 'mediazilla','http://bugzilla.wikimedia.org/$1',1),

Updated in r61487. Marking this FIXED.

No longer needs the "needs-review" keyword, since there is/never was a patch attached.