Looking at new 5th wheels....does anyone build a ?????

Check out New Horizons.

Maybe start looking at non conventional floorplans.
Front living or even front kitchens like this Keystone.
front kitchen Alpine
This was longer than you wan, but there are some shorter front living models from Heartland and others.

edit add, not a u shaped dinette, but does seat six and closer to your preferred length.
Sprinter

https://forestriverinc.com/rvs/travel-trailers-and-fifth-wheels/rockwood-signature/8291RK/5176
A little longer but would work.

A 3 slide unit would normally give you opposing main room slides and plenty of room to move around with an island. The island does add a ton more counter space and kitchen storage.

Like this.

Longer than what your requirements are, but everything else fits your criteria. Click here.

We have a Montana High Country 5er with the front living room. The opposing couches fold out to become beds. In our 5er, the 2 couches can sleep 4 people. Looks like this floor plan has the same arrangement, so you could sleep 6 easily.

I've not seen this specific model, but I have seen other Alpines with the upper kitchen with the full wrap around dinette. They are impressive. We first saw this in an Alpine (front kitchen), and were so impressed with it, we ended up getting the front living room in a Montana model because we did NOT want the center island either.

Good luck in your search. You may have to go longer to get what you want. But the bottom line is, get something comfortable for YOU and your "significant other" and don't worry about guests ... at all. They can always sleep on the floor in blow up mattresses and be tickled pink!

Here's a YouTube video on this model, you might enjoy: Click here.

OK, thanks for the replies and the help. Unfortunately, I am afraid some of those options shown above are out of our price range.

Thanks again.

clicky link
Floorplans and models can change each year or some times in mid year so I find its best to look mfg websites for whats available. Plug in the coffee maker and spend some time looking at mfg websites.

If you can find something close to what you want it sure wouldn't be hard to build your own dinette. Even removing an island would be relatively easy in many cases.

Cedar Creek Silverback 29RE (Dealer Stock Only)
You probably can get a booth dinette instead of the table.