What about the suggestion I made yesterday, about
using the standard link
syntax, potentially with an extra symbol at the beginning? So {{Test}}
means transclude, [[Template:Test]] means link to and [[#Test]] (or
[[#Template:Test]] if you like) means link to a special page, showing the
rendered template.
Of course, I've now realised that # is not a suitable character for this, as
although it is invalid in page names, it is valid in links as an in-page
link, so maybe another character would need to be used (how about question
mark?) Or perhaps use [[Test#]] instead?
I think parameters get confusing with such a syntax. Presumably they
would be separated by |'s, but then so is the display text in links,
so how do you know if the last section is a param or display text?