Functional toilet only bathroom size??

I'm trying to figure out what the smallest functional size for a toilet only bathroom. My current sketch has a "room" where the V and side wall form a trapaziod for some extra shoulder room. The space is 24" at the back 36" at the "door" and 36" deep. I might end up using one of those swing out shower curtain rods for the door to gain some standing space. Privacy won't be ideal but hell it's a small trailer and it's just the wife and kids with me. Hopefully this will only be occasional kid use and night time needs.
Is this too small to be functional with a portable toilet? I was planning on placing the toilet on a platform for extra height is needed.
Thanks
Is this too small to be functional with a portable toilet? I was planning on placing the toilet on a platform for extra height is needed.
Thanks