Some time back I wrote a PAM process, launched on copying a CR template, which scans Summary and Description for 'tags' comprising '#<property label>#', then substitutes the relevant property value for the tag. It worked quite well. You could do something similar in spel, or using a 'remote reference' calling pdm_perl and pdm_load - depending on which technology you prefer to engage :-).
Jerome's point is entirely valid - what happens if someone updates a property after this substitution has been done? So you also fire the process on a property update, look up the template and repeat the substitution, and too bad if someone has added extra text to the summary or description...
Hope that helps!
Regards,
James