I guess what it really comes down to is image scale more so than focal length. Taking weight and money out of the question entirely, an ASA 14" F/3.6 Newt with a FLI-16803 will give an image scale of 1.45"/pixel. It is all about matching telescope and camera.
So far I am managed 5 minute subs with a FWHM of 1.7 at 1.158"/pixel, not entirely sure if that is seeing or telescope limited, suppose I'll never know unless I get some truly amazing seeing
So the simple answer to your question, yes, you can get a bigger telescope
