If you're going to give a site as a design competition feature (as opposed to just describing a hypothetical site and giving other criteria), it should make some sense. What can one consider about this site? If you know Crissy Field at all, it's not that it happens to be a public space. Pretend it isn't. It is just a flat site with an obvious view, but very idiosyncratic siting given the neighborhood and other features (freeway overpass,biking trails, "historic" structures);and loaded local planning issues. It would be like "Consider that you are to build a house here, but ignore everything except the view and private beach." Because otherwise... IT DOESN'T MAKE SENSE! Also if I owned that piece of land, I'd dream of letting it be a park. I don't think I'd want to do the competition. I'd get depressed.
That's it. I'd build a tiny caretakers cottage and sweep the walks in the park the rest of my days.
I guess I just said what you were saying. Sorry.
Interesting that the Presidio Park itself is the site of several hotly contended development issues with other colorful players like GAP owners and Disney. Actually a very rich planning / architectural discussion /controversy. Somebody(s) will write a book or two.