There's no point in having an image scale that's smaller than around 1/3 of your seeing. You won't get any better resolution and you'll need more imaging time to get the same SNR. For long focal length I'm running at 0.67 arcsec/pixel and I don't often get seeing that justifies it.
The cameras vary quite a lot in weight but generally a camera with a bigger sensor will be heavier, especially if it has heavy duty cooling. Have a look at some camera specs and see how they compare with the capacity of the focuser. My Apogee U16M and filter wheel is 5 or 6 Kg
