Wow, lots of opinions here, and 2 or 3 of them are even applicable to the question I asked!
ForcedInduction, I agree that the oil cooler is there for a reason, or even multiple reasons, such as Florida, Texas, Arizona, etc... there are many places in the U.S. that are warmer than Germany, where an oil cooler is necessary. I'm still not convinced that Maine is one of those places... and if you're serious about that bet, you owe me $20.
And like I said in the original post, I wouldn't put a bypass filter in the place of the oil cooler without first removing or disabling the oil thermostat, so no worries there.
Stevo, nice to hear that your 240Ds are doing well without oil coolers. What kind of engine temperatures are you seeing during the summer? Have they ever seemed to be in danger of overheating?
Tangent, good idea, I had considered using hose clamps as a temporary fix, not sure if I'd trust them in the long run, though. I'd feel safer either putting new hoses in, or cutting them out completely.
Nate