This sort of thing can help in limited ways, say for scouting a location, but, if you use a different camera for the test shot, then you lose the advantages of being able to test your shutter, making sure you've remembered to include bellows factor and determined exposure accurately, and seeing the effects of camera movements and the DOF of the actual lens and aperture on the Polaroid. In other words, you can catch more potential problems with a Polaroid.

There's also the issue that these P&S cameras don't offer much manual control, and ones that do often don't stop down past around f:8, so you need to think in terms of ND filters if you want the exposure time to be in the ballpark of the real exposure.

If you just want to consider framing possibilities, you can make a simple composition tool out of two L-shaped pieces of cardboard, or learn to use your hands for this purpose, or if you want to get fancy use a Linhof zoom finder.