You got it right with the service frequency requirements.
This would not put me off to buy the car, I would at least try to see it. After all we are talking about 2 missing oil changes on a reliable engine. So what you want to find out is if the car shows other signs of "mistreatments" else than the poor servicing...
Try to find out the number of owners: is it a first-hand car owned by someone not aware of the 2 years service requirement, but treated the rest of the car properly, or was it owned several times by careless people just willing to have fun before selling it again?
How looks the interior, how does the car feels on the road and how does the engine sound? Get a good mechanic with you if you don't feel comfortable.
Don't forget as well the car is 10 years old, there are other areas that require good inspection if the car was not maintained regularly. (suspension, control arms, exhaust, air conditionning maybe, etc...).
You may even want to contact the dealership where it was serviced, ask them what they think of it or if they even know the car? (can always try although, we all know what to expect from BMW aftersale service...).
Good luck!