To doula or not to doula?

With our due date fast approaching,  5 days to be exact, it's time to make the final decisions regarding my labor experience.

We have taken the birth preparation classes and watched the educational documentaries trying to decide our best course of action. It became apparent that above all else I want a safe delivery with as little medical intervention as possible.

Having a natural birth is the most appealing option, but as a first time mom (with my own minor medical complications) I want to have a hospital team available to me at a moment's notice.

So, do I add a doula to the team?

Pros:
I have a condition called vaso dysautonomia that affects my circulation and causes me to have sudden low blood pressure  and fainting spells. A drop in blood pressure can be cause for an emergency c-section. If I have a doula she could be an advocate for me, if the situation occurs, she could let me know if we are truly in an emergency situation or if I have more time to attempt to do things naturally. she can speak directly to the doctor on my behalf.

She can help me feel focused and provide pain management techniques.

She can assist in helping my husband be as supportive as possible and also give him freedom by stepping in when needed.

My mother advised she feels ok about not being in the delivery room if we have a coach (max 2 ppl limit)

Cons:
The cost.

Redundancy in her role vs the midwives that are provided by the hospital.

Effectiveness: she is a stranger to me and I may not respond to her positively when in the throws of labor.

Does anyone have experience with doulas?