Here is what I would do if it were me:
1. Use regular WP
2. Download the WP code and make any changes in that code you want to make. For example, WP already creates a page and post with sample content when installed. It also creates a default category and default blogroll with sample links. You could find the file that does this...I think it's something like upgradeschema.php, but just search for it and make any changes in that file you want to the default page/post/category/blogroll...you could also add new pages/posts/categories and even blogrolls there to be created upon installing the blog. (Of course, you could do this in mu as well)
3. Upload the theme you want to start with, delete all others, and name yours default. Make any changes to the theme you want.
4. Upload any plugins you want to use.
Then use this wordpress code as your code for creating all new blogs...simply copy past the code (of course, with different name) and open the config.php file in each new instance and change the table prefix...you can even use the same database. When you go through the install, you will set yourself (franchiser) as the default admin and create an additional admin account for the user. While you are there, activate the plugins and you are ready to go.
I used to do this with hundreds of individual WP installs before I started using MU and I could create a hundred blogs in about 30 minutes...the only reason I switched to mu is because I do create hundreds of blogs on an ongoing basis and it's just easier with Mu...if I were doing 10/20/30... I would still use regular WP.
However, having said this, you can certainly do what you are wanting to do with Mu. It's just a matter of getting familiar with the Mu interface. As far as having a central login to the backend of all blogs, there really isn't much difference between logging into 20 individual WP blogs vs getting to the backend of 20 blogs through Mu. In Mu you login once, but to get to the backend of an individual blog, you still need to go to "site admin/blogs find the blog and click on the "backend" link...you repeat the process to get to the backend of the other blogs.
Okay...I've typed way too much...hope this helps...
Steve