Please describe in detail what a new manager does that is different than a blog. Then maybe some day I can improve the blog to meet your needs. They seem very similar to me so why build 2 features.
I do plan to revamp the File Manager and Shared files when I have time.
A developer can create a custom package and make whatever features available or not available as he likes by removing setup files. The setup page is really only creating/udating schemas and config settings in the db based on files. For simplicity and support reasons I package it with all the common features configured.
However the software itself is already installed before setup runs. There are .aspx pages and .ascx files and C# compiled into dlls in the bin folder that make up the installation and this is not managed by the setup page. The files are installed by a more priveledged ftp user, we don't want the web process running with permissions to install dlls or executable files so our setup page is not involved with that aspect of setup. Most of the features are combined into the same set of dlls mojoPortal.Features.UI.dll, mojoPortal.Features.Business.dll, and mojoPortal.Features.Data.dll. So even though you could remove the setup files and config files to make a feature not available the code for the feature is still there.
Overall, I think the I have found the right balance for the setup system. It installs what the package is configured to install, developers can leave stuff out in making their own packages. Our setup system avoids a lot of complexity and fits well with our security views. I do not think having more features installed hurts perfomance unless there is a bad performing feature but not as a factor of the number of features installed. The only resources which can be saved are disk space which is very cheap so while it may be a factor for some its not a prevailing factor. Giving the user choices about what to install is not going to save disk space because the files are already on disk before setup can run (as mentioned before our setup system is not invloved in deploying files).