Currently the only parameter input method is just a field that can be typed in freely. I am suggesting that is implemented in the template data editor. Basically you should be able to select an "Input type", these would include:
Field; This is the current input type
Boolean; A checkbox that changes the parameter to True or False
Multiple Choice; A dropdown menu with custom choices (Changes the parameter to the choice selected/the default choice which can be chosen)
Numerical; Won't allow the template to be changed/inserted unless it only contains numbers. (Could still be changed to letters or symbols in the Source Editor)
I think this could help simplify templates and help keeping templates the same from page-to-page