How do you avoid a large service who sends the on-call doc to your birth? I'd like my doc to attend.

Difficult. All ob/gyns must have some sort of coverage, even if they intend to come to most deliveries. No doc can be available 100% of the time. While having one's own doc there has emotional benefit, having a well rested doctor ready to fully engage any issue is also important. You might like to seek care with a midwife group, which are usually less busy and more likely to be at specific deliveries.
My doc at Delivery. All doctors have to have some sort of call group--no one can be ready 100% of the time. If having your doctor be at delivery is important, induction can be one way to arrange this. Also, small groups or solo docs often cover their own call during the week, giving you a better chance of seeing them at your delivery. Don't be afraid to ask your doctor what arrangement can be made.