Has enough spots for my taste already. I think you are looking to improve size and form with the WC cross, not spots.
I'm pretty sure the roth cross would be painful to bloom. I've got similar breeding purchased no less than 10 years ago that has still never bloomed. It sounded like a good idea at the time, I'm sure.
I think all of the bulldogs are tetraploid at best, but probably aneuploid (not an evenly divisible chromosome count). Some individual chromosomes might be 4 copies, some two, some three, etc... I could be completely wrong, I don't know where I heard that. I'd like to see the actual chromosome spread on these... Somebody go do that real quick! *grin*