Sounds way too complex for the use of templates to me. I would investigate server side includes (ssi) to refresh certainly the
navigation and title bar.
With server side includes you only update and upload one file whereas with a template system you have to upload every single page again after (if) the changes take effect. Templates should be reserved for basic simple sites of no more than 30 pages in my personal opinion (and that's pushing it a bit)
I'm pretty anal about keeping my code in order and whenever I've used templates I've found some pages don't update. It's then a nightmare to sort out which have updated and which have not. To change the pages that have not updated requires detaching it from the template to gain access to the code which is locked and defeats the use of Templates.
Dunno, if I was undertaking a big project I'd certainly look at a different more consistant and reliable method than DW templates.
Well my personal opinions is that you create to much layouts for one site (5 why?).
One good chosen design is enough I always try to convince myself and others. You can then always make some variations with some page elements like boxes etc .etc. which you can keep in a seperate css file called page_elements.css. KISS, keep it simple and stupid can be complex enough.
If its a big site with different portals I would create one template for each portal if they actually need to differ that much, and as allready mentioned maybe use server side includes.
But its just my opinion of course...
You can then always make some variations with some page elements like boxes etc .etc. which you can keep in a seperate css file called page_elements.css
Does this mean I can attach two or more style sheets to any given page? - may sound obvious but just want to clarify.
Or would I be better having a different css shet attached to each template?
Well if you create a page from a template you still can add more stylesheets to that page.
What I always do is create a template with one sheet for the main-layout and add another one for page elements that I use very often. But still your free to add css files to any page created from that template.