Acoustic Guitar Construction

Is the typical 'belly bridge' about the minimum safe width for an acoustic guitar? What are the considerations? And while we are at it - would extending the length a bit for aesthetic reasons be less than prudent?

Since the bridge and bridge plate have dual functions and serve as a braces too, I'd say that its important that the wings extend over the "X" legs. Seems 1" is the magic number for minimum width. Factors to consider are support at the front edge of the saddle to prevent string leverage from splitting off that section. Also you need enough room to have a reasonable angle of attack for the strings coming out of the peg holes over the saddle. And there is the issue of cracks along the center line of the pin holes, angling the holes to match the saddle slant is a help in this regard.

Hitting the X-brace with the wings is definitely important.
Another factor to consider is weight. You don't want to make your bridge too heavy or you will kill the initial attack of the string and the volume. You will gain sustain, but at a price. I think it would be helpful to see a picture of what you are thinking of, and then we can mock you...umm...I mean, help you fix any potential design flaws.
Somogyi uses a very thin bridge plate, but he also uses a large bridge plate to compensate for that. His large bridge plate also helps prevent the sound board from bulging behind the bridge since he uses very light bracing. I think the point of mentioning this is that if you alter one element of a design, you need to compensate for that elsewhere. So if you use a bridge design that is very short going from neck to tail, you might want to beef up the bridge plate to compensate for potential bridge roll resulting from the shorter bridge. If you make the bridge narrower from side to side, you will need to close the x-brace to make sure the wings of the bridge hit it. There is the potential for a loss of tone, volume, etc if you miss the x-brace with the bridge. Also there is potential for more bridge roll and catastrophic failure, but it's the tone that we care about, right?
Post some pics Dave. I would love to see your design.
Oh, and making it longer from neck to tail, that should not hurt anything other than adding weight, which I addressed earlier in this post.

The archtop guys and gypsy guys can get away with a long (side to side) and narrow (front to back) bridge because all the pressure is downward - most of it, anyway - and the design fits with their ladder-braced instruments.

I want to keep the aesthetic shape because it really works for me, but if I use a typical glue-down bridge it ain't gonna happen. So I'm trying to come up with a narrow configuration that is also maybe 8" long and does not constrict the top any more than necessary. In other words, I want to come as close to this instrument visually as I can, but with a fixed bridge, and obviously no tailpiece. Which is a shame because it all works together so well.

If the top will be spruce, you could inlay a spruce piece on the back of the bridge so that from the front, the guitar would LOOK like the one you posted, but it would still have a traditional bridge. You could also use white bridge pins to blend in with the spruce piece. Visually, it will appear to be a thin, arch top style bridge, but functionally, it will be fine. Do you catch my drift, man? Something like this:



Now do you see what I mean?

Well, it would be pretty difficult NOT to see what you mean, man.

I do see it, and that is in the right direction and I thank you for the tipperoo, Tony! I will do some - what I loosely call 'thinking' - about that approach, it might work just fine. :-)

Glad I could help.