Use 1 FBX and change in Unity or multiple FBXs done in Maya

Hi all,

Say I've got this model of a house made in Maya.
I want to use this model several times in Unity to make a row of identical houses.
However, I want to make some subtle changes to each house, say open some windows, so that each house look a little different. No changes in geometry, only change the orientation of a few sub-meshes.
At the same time I would like to preserve my workflow (Maya-Unity-Maya etc) as long as possible. So that when I want to change something in the geometry in Maya I do not have to redo everything again in Unity.

What would be better:

1) Use 1 FBX as base model and make the window changes in Unity. Redoing these is I really need to go back to Maya
2) Create multiple instances of the FBX from Maya each with their own specific little changes.

Note that I do not mind if my project size gets a bit bigger because of the additional FBXs. I'm only running on big desktops so that should be okay.

What is the impact on Unity and performance with each of these options?

Thanks every so much for any help!

Marco