I definitely like the idea of having a single template instead of four.
The current design looks a bit weird depending on browser size. When I visit the example page, the four divs each have a different height:

That's probably fixable. However, as you point out, the "four" can easily become "or more" in the future. There's not really room for any more boxes horizontally. So I'm fundamentally uneasy with this layout. Plus, I just don't think it really looks good beneath the other templates on the example page.
I'm having a hard time visualizing what you mean for the single column option. I guess my brainmeats are too tired right now.

I'll see if I can't come up with some suggestions for alternatives. Meanwhile I'd be interested in seeing an example of your alternate layout.