Good ways to create pinball table lights?

I making a pinball game and trying to figure out how to make lights in table, lights with: arrows, text, 2x, 3x, 4x , etc...

I planning to make "floor" of table with simple flat mesh and one texture. What could be good way to make individual lights to turn off/on. One idea that I have is to use projectors to project texture on lights that are turned on. But then I would need something like 20-50 projectors with individual textures and don't know if I run performance problems that way. And I haven't figured any easy way to place those projectors

Ideal solution could be some kind of dynamic texture creation, an image with layers and then adjust opacity/alpha of layers based on which lights should be on/off. Calculate the image and then assign texture to table floor material. But I don't have any good ideas how to achieve this.

I'm using free version of Unity and targeting to make game that performs in web player, but like to have solution that could be ported to phones/pads with out too much tweaking.

// Edit: I think I will create flat polygons over table (decals?) that have texture of lights turned on, then turn those polygons on/off. Probably use prarticle/additive material so I can make lights overlap.