How to use multiple render textures and cameras?

Question

I simply need to write text on 3D sphere. But I want to change it at runtime as I want. So, using a premade material is not an option.

I tried to make this with render texture it works pretty well but when it comes to multiple objects with multiple different text I noticed I need multiple render textures, cameras and layers so that the texts in front of the cameras do not interfere with each other. But unity gives only 32 layers. I don't know how many object will be generated and create layer. It doesn't seem like a good practice.

Is there another way like render texture or is there a way to use render texture for different texts?