Or is it impossible to cause a Computer to create an Archon with 2 Templars?

Pretty much impossible to get them to deliberately do it. Archon Warp is governed by unit production orders, rather than 'spells AI' like most other abilities. So you have to run a custom game or campaign AI script to get them to create archons and generally this isn't appropriate for UMS maps.

Ref: http://www.staredit.net/topic/13823/