Jeffery
A quick search will bring you up to speed on the history of this request. I know of more than one firm that will not consider VWL until there is a valid irrigation module. Especially in this time of water conservation.
However, look at these links to see what "real" irrigation software looks like.
http://www.sciencehill.net/
http://www.softwarerepublic.com/irrigationsoftware/
http://www.watermark-id.com/
http://www.eaglepoint.com/solutions/workflow/office/landscape/
http://www.wcadi.org/
What VWL presently has is a system of symbols. For irrigation design, we need the intelligence that will allow for pipe sizing routines, hydraulics, valve sizing, coverage analysis, etc.
When you look at the above programs, you will see a common theme with the offerings.