Yep, you can link directly to a specific item on the order form. Mike's right, it will just make the item pre-selected on the order form though, at least for the ajax one. I have to check, but for the wizard type, you may be able to link to the 2nd page where you configure a specific item. If so, this would bypass the package selector and go straight to configuration which may be preferable.
The new "default" order template in 3.2 will be Wizard Boxes, I think it's likely to be the most used order form.