combine deferred and forward rendering

We want to use deferred lighting with a custom (toon) lighting model which unfortunately doesn't work as we can't have custom lighting calculation but can only modify the final light color. One alternative we thought of is to combine a forward rendering pass with a custom lighting model with a deferred lighting pass with default lighting model for smaller lights.

Can we combine deferred and forward rendering into on depth and color buffer? If so how? Has anyone tried it?