How do I wire challenging bath situation
You can do it using only 12/2 and 12/3 cables like this.



Or you could use 12/2 and 12/4 cables like this.



Because there will be so many wires in the box, you'll want to get at least a 34 cu. in. double gang box.  Like this one.

NOTES:  


I've excluded grounding conductors from the images to increase clarity. Do not forget to connect all grounding conductors.
These images assume the incoming power feeds into the switch box.
These images assume that both switches are in the same box.