Plumber needed for help with Tiny Home Design

Hello!

I am building my tiny home from scratch! I'm just finishing up the floor plan/design and I am trying to accommodate where my plumbing will go. Its a 28 ft PAD trailer from Iron Eagle that I am building off of and the tiny home will be both off-grid capable and able to hook-up to RV hook-ups. I will have a shower, energy efficient washer, energy efficient dishwasher, bathroom sink, kitchen sink and refrigerator(probably doesn't need a water hookup). I would also like to put plumbing in for a toilet, though I will be using a composting toilet at this time. 

I need help designing the plumbing, where the fresh water tank will go, how big the fresh water tank should be, grey water drainage and collection, hookups for washer and dishwasher, P piping to reduce smells (Or other mechanisms), and if I can use a gravity fed system or if the fresh water tank needs to be underneath and a pump installed. 

This tiny home is my dream and I can be flexible and change the design plan around a little to accommodate the appropriate plumbing needs, but I need your help!

If this arrangement works out, I will also need a plumber to help me put it together when I am framing my house. 

This posting is for help ASAP. The design is ready and before I send it off to the certifying body I need to factor in plumbing. I am itching to move onto buying the things and ordering the parts to start building. Come contribute to tiny house building!