I’m not a projectionist, so others here might have more to add, but I’d look into doing this with a single 16:9 projector stack, overscanning your screen. I’d think that the amount of keystoning that you’re suggesting will make blending a challenge.
A system like Vista Spyder or Barco Encore will handle the blending and allow you to arrange your video sources on your screen, either full-screen or as PIPs.
Blended widescreen is complicated. There are many considerations here, depending on your physical space, budget, and requirements, and I think you’d be well-served to hire an integrator to help you evaluate your options.
Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events