I take on board what you're saying Nick, and I'm not saying it isn't doable, but I think there's a difference between right size for cinema and right size for TV.
For cinema and 1080P you're looking at distance to screen as 1.7 times width to ensure benefit of HD, and then no more than 1.54 to get an image big enough for immersion, (I believe this gives the 30 degree viewing angle and is the angle recommend for a person 2/ 3 toward back of cinema), and with 1.2 being the maximum closeness, (think this is 45 degrees). I have all the figures somewhere from when I calculated my screen. You have to factor in a bit where you like to be in a cinema, as you may prefer a smaller or larger image.
But if you have this right for cinema, it doesn't mean that it is OK for TV. I think I have mine just about perfect for me for films, but oput the news on, or a Tv programme and massive heads filling the screen isn't what i want or exciting. Sport is fine, but normal TV tends to focus more on clise-ups and shorter shots, and it isn't as good, and isn't to the same quality, even upscaled, as HD BulRay films, (unless you stick an HD channel on obviously).
If you factored in TV shooting and upscaling, you'd end up with a much smaller picture, and it would be brighter, yes, but for films you'd lose the cinematic feel. I guess losing the impact is a personal thing, but for me it becamse less special if I used the projector too much.
Using the memory feature for a different sized picture from the proejctor is intiguing, but it looks a bit rubbish to have a smaller image inside a frame, and if a lot of the time you weren't using the real estate, a bit of a nuisance having a big screen rolled out or in place.
Accept a splitter and TV can enable you to have the flexibility, but that's what I'm suggesting, and what I've got. Although if it was just the case of needing channel flicking or scheduling recordings, there are web sites that let you view the TV guide and some PVRs let you schedule recordings over a web interface.
For me, (and some of this is personal experience, but I want the poster to be aware of possible issues), the TV and a projector is good. I can stick the TV on without worrying to see if anything takes my fancy, or to set recordings, have bright lights on to read or see other things while casually watching, or watch TV in bright sunlight. For films and big sport events I get the big screen on.
I think DJ Krime's projector / TV combo sounds very good!