Of all of the things I loathe in a day, it's making sure that all of my plugins are up to date, and/or uploaded to each separate plug-in folder on each blog.
1) To be able to create a plug-in repository that contains all of the plug-ins that I like to use on any given blog that I operate. From that repository I can connect to each blog. On the plug-in tab for each blog, I can simply select from a list of plug-ins that I wish to make available to that blog. On the blog repository, I can also select on each plug-in which blog it should connect to.
2) To be able to have one dashboard for all of my blogs. Much like I select a category or categories to post my articles to, I would like to be able to select which blogs either a) display which categories or b) also receive the post that I'm currently writing.
When I write an article that I would like to be syndicated across multiple blogs, it seems to me that selecting "blog a and blog b" while writing would be more efficient.
I guess centralizing a multi-blog database would be the best option, but that's above me.