Once upon a time, when I was an itty bitty undergrad, a prof told me that "99% of directing is correcting the mistakes you make in casting." I'm not sure how true I've found that to be over the years, especially because I'm very arrogant and have never felt like I've made a mistake in casting, but there is no doubt that casting a show is one of the most pivotal things that happens during the process. You want to find skilled, experienced people who are committed to the project, and those columns don't necessarily line up. Especially for something like this where the budget is still being worked out. In a situation where you can pay people more than peanuts, you can rely on their commitment to a pay check, at least. Usually.
I've got a little bit of an advantage being in a program designed to teach people how to produce this kind of theatre, and as more and more people have moved from expressing interest to wanting to sign up, I find myself in the position of having to put together a partial cast list. I really hate this part. The only thing I hate more than casting is auditions, which is really nothing more than the part of casting where you make your mistakes (on either side of the table). An actor never gives you their best work in auditions, and if they do, they (and possibly you and everyone else involved) suddenly have bigger problems to worry about.
Fortunately, I'm not going to have to do auditions. I've seen just about everyone's work, and one of my key partners on this project has worked with just about everyone else in the program, and can offer me insight into their strengths and weaknesses. Invariably, she's made me feel better about the pool of people I'm drawing on. Still, I have to make some preliminary decisions, and fairly quickly. I don't know if there's any way around getting some of these folks to sit down together in a room and read from the script.