Sub FrontendTemplates within modules

I'd like to throw an idea about with the current design of a few modules, some modules (mostly Calendar ones) will create instances of FrontendTemplate within for loops and parse them within compile().
Thus if you want to bolt on additional functionality this becomes quite tricky.

In some cases an effective hack can be achieved by putting a %s in the sub-template and then using sprintf on the parsed code.
In others you have to copy the entire module contents and make changes where needed.

A solution such as a new hook preParseFrontendTemplate is needed, so that changes can be made to the sub-templates before they are parsed.
Or no parsing of the inner templates should be done within compile(), instead give the templates a chance to be added to before parsing.

Why is this needed?
A lot of my work is taking existing modules and adding functionality, my ideal situation is where I extend a current module. Then either replace the module or name the new one something else.