The midwife will be able to be there and support you for your whole entire labour. The OB will just deliver and maybe come in and check on you sporadically for a few minutes.
The other option is a doula.
I'd get the midwife at least.
If you want both an OBGYN and a Midwife, then go ahead! You should be comfortable with who is delivering your baby and confident in their abilities. I've heard of a lot of people who had a midwife and OBGYN at their deliveries so It should be no problem for you.
I think you should check out this site, it's about pregnancy and Subutex/Suboxone use
http://hubpages.com/hub/Pregnant-or-Breastfeeding-Buprenorphine-Suboxone--Subutex-or-Methadone---Safe-for-Baby-and-Mom
I definitely would not try and get off the Subetex cold turkey as this will add a lot of stress and can cause miscarriage. From what i understand(not an expert here lol) most babies are actually born with an addiction to it, if it's used during pregnancy. So i would go with your doc and try your best to lower what you intake