I'm a bass player but I dabble in guitar.If I put a 6 stringed bass neck on a guitar would it affect the sound at all ?
The spacing of bass guitar strings, and their thickness , means that the neck, aspeciallly a 6 string bass neck, will be a lot wider than that of the original guitar where it joins the body. It will probably mean the strings are not exactly aligned with the pup poles. There will be major surgery to do. That in itself will slightly affect the sound.
Having a longer neck will add more wood, so may give a little more sustain, but it will hardly be noticeable. With different strings, or the same strings tuned differently - otherwise the originals would be too tight - will affect the sound, too.
A bigger problem is going to be intonation, as the bridge will most likely be in the wrong position - 12th fret needs to be half way between bridge and nut.After that, the machine heads won't be suitable for the thin strings. It just goes on - and on... but, by all means try it, you'll only end up with two wrecked guitar/basses at worst.
Seems like you are trying to make a baritone guitar - maybe try one out before embarking on this venture.