Unity 4.3 Any chance Sprite mesh will become accessible in futur update ?

I'm not sure if this will help you but I just discovered that it is possible to force Sprites to use a full rect mesh rather than the tight "optimized" mesh. This solved my problem with sprites not playing well with my shader, but doesn't give you the ability to supply an arbitrary mesh.

In the in the texture import settings (http://docs.unity3d.com/Documentation/Components/class-Texture2D.html): 1. Select Texture Type "Sprite" as normal 2. Configure the basic sprite properties 3. Change the Texture Type to "Advanced" 4. Find the Mesh Type property and change it to "Full Rect"

I think access to that setting is PRO only, but the optimized mesh generation is also a PRO only feature so it might not matter.