I've been asked to use projectors instead of gobos a couple of times, and it never seems to work to anyone's expectations. I personally think that this mode of thought comes from the client's (or worse, our salespeople's) idea of "why spend money on a gobo when we can do it in Powerpoint for free. The projector never "pops" the way they envision it will, and to put a projector that would do the job in there (15,000+ lumens) would be more expensive than the gobo itself. Then there's the issue that you will in most cases see the edges of the projected area, as you cannot project black.
I will always recommend a gobo, either glass or metal, depending on the complexity of the graphic, and a Mac 2K performer or better. That's really the best way without really spending some big money on the effect.
For better or for worse, we are not generally content providers, and it's very rare that we are asked to be. So for a Sunrise/sunset effect, I would either do it with lights, again, 4 to 6 Mac 2Ks would probably do that well, or the client's got a video production person with a stock footage library or similiar resources to create that content, then you are only on the hook for the display.
I would still be nervous (in the general terms as I understand your question) about the brightness of the projector and the surface available to project against.
Hope that helps.