[Mediawiki-l] Strategy: Best way to use customized wiki? UserSkin vs. Monobook

[elucubrator at web.de]

thank you for taking the time - i try to be precise

Situation:
a) our task is to set up new wikis all the time which should be based on an individual design
b) my task is to provide the admins with a custom design
c) we have to handle all the future upgrades of wikimedia on all those wikis

Problem:
After initial fiddling with the monobook and cross browser problems i came up with a design on a working wiki.
Now the Admins need a "package" from me for further installations of new wikis.
They have to support those wikis and therefore they need to update/upgrade all those wikis.
We need the best strategy to create a custom design under this point of view.

Theory:
Obviously it is easier to re-install a user skin
than to sync all your individual changes with base design 
after an regular upgrade of the wiki software 
(which I will have to do on a growing number of wikis regularly)

Question:
I need to make sure, every user sees the customized design immediately.
a) Can I (and how do I) make a skin the default view for the wiki and 
b) prevent the user from changing it

What I check so far:
a) I can completely disable user skins.
b) many people just do their changes on the monobook etc. - 
but how do you handle the regular upgrades best then?
c) I understand I need to do a lot of cross browser compatibility fiddling :-(

Thanks for your input