I would set it up to be as natural as possible and then dial the GI lighting values to get what you want.

1.)  Use a distant light with the soft shadows jacked up big.  Start at 100 ft (for the soft shadow radius) and increase it until you get what you want.

2.)  Put in a skydome using a bi-gradient in the background.

3.)  Turn on the skylight and indirect light in the GI settings.

Then dial the strength of the lighting for each of the two GI effects and see if that works for you.

The result should actualy be physically realistic.  If it's too dark, that means that you need more lights inside just like real life.  Add them.  That's why we have lights indoors.  If you have to have lights inside, it won't look weird.

-Kix