To add to the excellent advice from Mike and Julian that you’ve gotten already:
I generally prefer Spyder to Encore because its architecture is more elegant and flexible, but I think it’s overkill for the show as you’ve described it. Encore was built to do exactly what you are describing and will be more cost-effective than Spyder.
Watchout is a great solution for feeding full-res backgrounds to a multi-image switcher, and I use Watchout all the time, but I’d hesitate to recommend it as a multi-image switcher itself. It works on a timeline metaphor, not a program/preview metaphor. This makes it great for canned shows that won’t change, but less practical for live events where you’d prefer some flexibility in switching. The new features in v4 go a long way towards addressing this concern, but it’s still not the same as a Spyder or Encore with easily recalled presets.
Also, when I use Watchout systems, we always spec a backup, so you’d want to double your estimate to 8 keys and systems. Although Watchout itself is very stable, I’m uncomfortable with the risk of a computer crash without a live backup during a show.
I’ve done shows with other systems as well, but as Julian mentioned, you will run into resource constraints; you may not be able to position PIPs in the blends, and you may not be able to transition from one source in a PIP to another depending on the number of M/Es in use, forcing you to clear one PIP out before bringing the next source back in. That doesn’t sound like a big deal on paper, but it really slows down your transitions at the event. In other words, you will save on budget, but your creative options onsite will be severely limited.
Finally, I’m not a projectionist, but will 8K projectors be bright enough? I would have guessed 15K as a starting point.
Walter Soyka, Principal
Keen Live, Inc.
Presentation, Motion Graphics & Widescreen Design
RenderBreak: A Blog on Innovation in Production