Playing a covenant of wizards in old school D&D?

I have always been fascinated with the game Ars Magica.  (free download of 4th edition rules is available at this link) The closest I ever came to playing it was a game where we were wizards in a post-apocalyptic setting with various robot and mutant animal underlings.  For that game we created characters in at least 2 different systems (neither one was the system published in Ars Magica) and just used whichever set of rules that was apropriate for the character in question to resolve actions. 

But that's not why I wanted to post today. 

I've been thinking about running an Ars Magica style game with a D&D type system.  Other folks have written about this here and here. The thing is, is that while I love the idea that Wizards are the main characters and that clerics and fighters and merchants or whatever are just the hired help, I'm not really excited about the intricate Ars Magica game system.  So, what if you just took that concept and used, oh I don't know, B/X D&D rules as written.  (or at least started with that and made as few changes from there as necessary)

You could start with Magic-users of high level to aproximate the power of Ars Magica characters, but I think it'd be more fun to start with 1st level wizards and build a covenant from the ground up. 
PCs can hire a bunch of mercenaries and shield-bearers and head into the dungeon looking for bits of magic. 

Change I would make to RAW:

• M-Us don't automaticaly gain spells when they gain a level, they have to find all their spells.
• Domain building starts right away, no need to wait until "name level".  These are wizards we are talking about here.
• Spell research and magic item creation and other non-dungeon activities including domain building can happen at the end of each session, to explain what the M-Us do in between dungeon expeditions.  I would suggest that unlike in D&D where spell scrolls are fairly common treasure, most of the time spells that are discovered in the dungeon are incomplete fragments and further research and experimentation is necessary to turn them into a spell in the wizards spell book.  This alows the DM to give the players a hint at the kind of spell they can make, but the PCs can take those fragments in whatever direction they want. 
• I would consider making spell casting times longer, maybe one round per level of the spell.  (in Ars Magica longer casting times reinforces the need for shield grogs)  With maybe an option to burn a spell slot of one level higher to speed cast. (this wouldn't come into play until 5th level when a MU could burn their 3rd level spell slot to get off a 2nd level spell in one round, and it wouldn't be super usefull until 7th level when a MU could burn their 4th level spell slot to speed cast fireball)
• I would also consider the option to cast an unmemorized spell, or a spell fragment or even a spontaneous spell made up on the spot like in AM,  but that's a pretty big divergence from rules as written...
• Retainer rules wouldn't need to be changed at all.  I like LotFPs retainer rules, where the charisma limit to hirelings effects NPCs with character levels or monsters only with no limit to 0 level hirelings.  Actually LotFP would be an all around great rules set to do this with.

I think it'd be awesome.