There are quite a few different ways to do this, but I would think the simplest would be just to put in one of the single gang switches that can do both single tap and double tap. Use the single tap for the fixture on the load to that switch and use the double tap as your “virtual” switch.
There are a couple of different Z wave switches that have come out in the last year or so that can do this, including the homeseer and one of the recent GE models.
The wiring is simple, it works well with SmartThings, and it sounds like it would give you what you want.
See also the following thread for discussion of this feature:
