Most of the garages in the game are tiny and not really suitable for an interior:
Wouldn't really be very realistic to walk into that and see this:
It's a nice idea I just don't think it would work very well. I don't know.
Why not make 3 versions?
1 A small garage, with some tools on the wall and the car, but not much more, for single slot garages in houses and seperate single slot garages
2 A 2 slots garage, more tools and a table and some random stuff, for bigger houses with 2 slots.
3 A 2-4 slot garage like the image shown. It would be good for very big garages, like those on mansions. 2 garage doors lead to the outside.
You could add a normal door as a exit/entry when on foot. But leave the exit doors on garages which actually have one outside, and make it so you can always enter throught the garages/sliding doors.