As a post in
http://modxcms.com/forums/index.php/topic,59238.0.html stated, I think it would be particularly beneficial to have a sort of "ala carte" installation package for certain components of a website.
Need a blog? Download the package, which includes the necessary plugins, chunks, etc. that are needed for a blog. Then, once installed, take the user to a page where they can turn on/off features from that package (comments, archives, related posts).
The possibilities could really take off. Shopping carts (think a custom installation of Vision Cart with only the options you need), Wayfinder configs for certain types of navigation menus (that can then be customized using CSS)...
I know some of this stuff is possible, but it’s a lot of work, especially if you aren’t a PHP developer. For those users just getting started and want a simple, easy to install CMS, this would be huge in my opinion.