Hi, this is irrelevant to your questions but I thought I mention one of the many ways to produce PDF output from your cards, e.g. for attaching to these email reports. This is of course LaTeX. It produces exceptional PDF/PS documents using a simple html-like (ok ok!) language which loves to be template-ed. You first need to install latex (TexLive will be called in your package manager) on your webserver. Then there are some Template plugins for it, e.g. Template::Latex (also Template::Plugin::Latex) and you have a Template-like interface to producing PDF files. The caveat is that you must now maintain both HTML and LaTeX templates. The latter is a pleasure though...
If there was a Nobel for Computer Programs, more than one would have been awarded to the humble, open-source and free TeX/LaTeX - created by a true scientist with an eye for aesthetics and detail.
Apropos your multiple templates dilemma. I would go with as many templates as possible if that would not hinder performance. For example, you can find out that card_call_center and card_sales have some common parts, let's say customer address. Well that part can be templated and re-used. Again, I don't know what effect this ultra-fine templating will have on performance.