Transfering Build Orders From 1 Unit to Another

I'm attempting to create a map where you are basically the god of your help -- you guide them and help them but have no actual interaction with them. To this extent, you basically need to add buildings to your workers build queue.. this is so that if the worker is currently occupied, you can't force him to stop and do something else.

By using the Build Small Tower ability from the Ivory Tower item, I can get the layout of a building and position it where I want it to be built -- the first problem being that there seems to not be an event to capture this. I tried the various effect, spell, build, etc generic unit events to no avail.

The second problem is anytime that I order my worker (a standard peasant, for now) to build anything that can be built (such as a town hall or scout tower) to a place that it can be built (it's "unbuildable" terrain, but I altered their Placement Requires to deselect the "Buildable" requirement), the game crashes! Like... poof!