That is really cool!!!
I actually made a very similar version back around Christmas. I had some extra Rex's laying around, and I made Echo and Fives using rex parts. I thought that if they were in the 501st, they most likely would adopt the unit colors.
Sometimes, I feel that Hasbro reads my mind.
Great paint application.
However, it appears that the handprint on Echo has 6 fingers.
Heard about your health issues, hope you feel better soon.