Hi,
I have recently published a game made with Unity that i've worked with Rendertexture and shaders and I can totally do what your developer has hinted.
I have more than 6 years exp with programming, including graphics programming, and can solve this issue easily.
Here is the link to the game that uses rendertexture and my own custom shader for the river flow maps and stencil buffering.
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Looking forward to this opportunity to deliver the solution for the success of your project.