How about good old MS Word?
I suppose it is not that nice presentation-wise (although I bet you could fool quite a few people with fullscreen print preview), but you do have much more control over the style vs. content. As long as there is no "manual" formatting used, you have some of the things you ask for... Namely, use of a template allows you to give an underlining style structure, it can be updated after the presentations are created, etc.
Other things you mentioned could be done as well (such photo sizing, cropping, aligning), but that would require writing several macros. However, once you have them, they can be attached to the same template so the users can apply them as required.
Edit: jumped in from the newsletter, didn't noticed it's quite old...