Some times ago I have ideas like your: automate MODx templates.
And I resolved this by adding special block in template description string like this:
This is Flat template {class=`unit` alias=`flat` children=`17,21` table=`realty` pagetitle=`%rooms%-room flat` grab=`Flat|Business flat`}
With plugin QM (QuickManager) I process all additional template params like "children" and "pagetitle".
And now I can easy set children template(s), pagetitle generation format, auto-alias, tablename (for Quid plugin), class (used by QM for manager interface auto-modification) and all I need.
If this conception is interesting to you, I can share sources and more information.
P.S. Speaking english so-so, hope you understand me.