It seems like you have your mind made up and you're looking for a justification for it. Or...maybe i'm reading into it too far.
Your average $7-9K E46 330 (what you will need to buy to be happy) will be 100K-130K miles, and worst case scenario, you have to plan on it needing the following to bring it up to speed and be something you can trust almost completely:
-Cooling system - $400
-Intake hoses, VCG, OFHG, and other things that will cause annoyances - $100
-Shocks - $500
-Front control arms and bushings - $500
-Fuel pump - $150
-DISA - $200
-Belts and pulleys - $100
-Fluids - $150
-Clutch&Flywheel - $800
TOTAL = $2900
That's not including consumables like brakes and tires if the car needs them. But figure on that being a worst case for money expenditure. If you want to keep the car for a while and be able to trust it...just bang most of that out in the first few months of having it (obviously not the clutch, or anything you know has been done). If you're only planning on having it for 2 years or less, I wouldn't bother with some of that stuff. It all depends.
But that's about it. I went through this with my E36. I spent like $3K in preventative maintenance on the car in the first year and a half I owned it. I haven't done much if any maintenance since then (2008 or so), outside of fluid changes, spark plugs, and that sort of thing. The car is dead nuts reliable. But it wouldn't be if I waited for stuff to break. I'm going through that process with my E46 right now.
You won't be saving much money if you own the car in the short term. But I hope that helps put a worst case into prospective for you.