Looks like a nice big space.
I'm not sure I would install the drain on the 45 like that but it could work out with the right tile layout.
What is your big wish list? Is there a natural grade to your bathroom?
What type of tile?
The step up look does open the doors to lots of options. If your framing with common lumber remember that you will still need to add waterproofing and grade into the calculations. Most lumber and plywood floors require you to add a good 1 3/8" of mortar.
Planning this step well could free up a lot of time if the floor was designed to accept Concrete Board or Green EBoard and then waterproofing.
I have quite a few examples of this look on my Houzz account - take some time and look at this ideabook and tell us which picture you like most.