I'm wanting to get away from the prefab base. That's what was originaly in there. I'm confident in my skill level to tackle this project as there isn't any rush

I wasn't refering to the 2 x 10 as a curb. There would be sections put in between the studs so I can climb the membrane up the walls 8" or so. The curb will be three 2 x4's stacked, as I believe this is typical.
Concerning the drain I'm just not sure what the best route to take is. Do I need to switch it to pvc? Can I use a coupler to go from cast to pvc?