Im curious and apprehensive to see one of these toys in person. I would like to know if a custom compartment could be added to the under carriage to seat four figures or so.
I get the sense from the Rouge One previews - and even the giant hanging cardboard U-Wing display I've seen at Walmart and other stores - that the U-Wing is a larger ship apparently with a cargo bay or troop compartment that has side doors and a ramp. The ship certainly is not as big as a light freighter like the Millennium Falcon, though it is likely larger than a standard star fighter like an X-Wing or Y-Wing. That said, the toy is almost certainly under scaled. The cockpit only holds one figure and if you were to remove the nerf gun and open up the underside, you could maybe hold 2-3 figures sitting only.
Here is a size comparison shot of the new U-Wing with the Legacy Collection Wedge Antilles X-Wing and another picture showing a profile view of the U-Wing with the Cassian Andor figure for size comparison:
The toy U-Wing appears longer than the X-Wing, but that is only the wings. Its fuselage, while somewhat beefier, is shorter. I am not saying that is how those ships compare in-scale since both toys are obviously out of scale...