David, I think you will find that the studios that are best equipped to deal with the kinds of sessions you are planning to conduct will also accommodate you EXACTLY to your liking! They will indeed have house engineers available, but certainly will NOT charge you for them unless you use them. The studios I have gone to where we were not using one of the house engineers, usually the owner himself (no, at a lot of the places the owner is NOT considered a staff engineer!), or the studio manager would come in and show us the ropes and make himself at our beck and call at no additional price throughout the session, or at least until we were comfortable. In the bigger studios, there will always be somebody around to assist you and your personal engineer. At the rates these places charge, they want you to have the most favorable opinion of them possible!

But I gotta tell you, it is grand to be treated like royalty in somebody else's studio!
Without fail, these more upscale studios don't have nearly the kinds of "idiosyncracies" alluded to earlier! If they do, and the session was slowed down because of it, or a quick work around was not offered immediately, the owners were always very gracious with discounts and would have the problem fixed before the next session! If we were renting gear and had to rent it an extra day, they would credit us EXTRA studio time that covered the cost of that rental!
If indeed you have a quality engineer that you are bringing in, he will very quickly figure out the studio with only a little bit of assistance from a staff engineer/second engineer from the studio. Once you get out of the home studio realm, you start seeing how the bigger places put almost everything on a patch bay!

Also, if your guy doesn't know how to use the console that is there, or read a spec sheet (yes, most places I have gone too have a book by the console documenting any modifications to the console), then maybe he is the wrong guy!
As to a studio that can accommodate your session, you have to remember that not every town is going to have a studio that can accommodate big sections of strings/orchestras. There simply is not enough call for that kind of session to justify the real estate required! Most studio at the most deal with maybe 9 or 10 session players at once, with many of them requiring isolation anyway! So, trying to bring in a orchestra to a studio that almost never gets a call for that kind of thing is rather silly eh?
I would imagine that most of the studios that can accommodate orchestras are probably located near movie studios because that is where most of the call for that kind of music is going to be! LA, New York! It might be worth it to fly to either to do your session. Also, because of the sheer numbers of session players in either area, you might actually get a better deal hiring from those areas! If anything, you will get a better bang for the buck, either better players for the same money, or the same quality of players for less! Worth checking out.
What you should be looking for possibly is a good quality mobile studio! The upper end mobile studios SHOULD have experience with orchestras and I think that they will also have an engineer who is experienced enough to be able to advise a bit concerning mic placement in a concert hall that will make your orchestral part fit into a more isolation orientated recording of a rock band. Generally, orchestras have closer section mics directly above the section, then the room mics. I'd imagine that it is a matter of mixing less of the room mics in the final mix that will help the orchestral parts fit in better, but I am no expert in this field.
