A friend of mine recently asked for advice on pitching himself to a group of developers for a project management spot at his gig. He was feeling the weightiness of asking to help manage a group of people who do work he doesn't deeply understand himself.
Rather than try to pitch them on projects he had successfully managed before, we talked about what I want, and I came up with this pitch:
you'll work to keep them from getting blindsided, which has some sub-points:
pushing on them to get as much understanding as to what needs to be done to communicate it to the customer (it can be a strength that you don't know too much about what they do. once you understand it, the customer can too).
not pushing into the unknown and forcing answers where they don't exist yet (e.g. no numbers in estimates, identifying amount of perceived risk in addition to perceived effort).
working out contingencies with them.
you'll defend their work environment to enable them to do their best work, tailored individually as much as possible.
you'll run interference for them transparently and tailored individually. I personally favor as little interference as possible. Others may want more. Running interference means reducing noise to increase signal, it doesn't mean making yourself a required part of every conversation. Every involvement you have costs something, so make the costs pay for themselves. Make your ideal this: that you're ultimately not involved at all, that the customers go directly to the people building the solutions at all times. Then work backwards from that. When you notice you're superfluous, get out of the way.