To have a top break revolver in an acceptable chambering, you'll need to design a good locking mechanism that takes stress off of the top strap when it's locked.
Webleys have lots of bent top straps due to bullets hammering the forcing cone of the barrel, trying their damnedest to open the action.
This could be alleviated by having a 6 o'clock barrel, however you run into some more problems - now you need an extractor and ejector. Because the barrel's in the way, you can't have the simple S&W or Webley methods - maybe a manual pushbutton that releases it?. Worse than that, you'll need to have a robust hinge - possibly around the barrel shroud to vaguely align it with the recoil force, though that's questionable for longevity.
There's a lot of time and money to be put into R&D, then getting a working prototype, shaving off excess, and getting it into production without it turning into the Remington R51.
Dreams are nice and all, but making a new gun is where optimism goes to die.