I like this list and use third party tools for a few features I want now (pathfinder as a better Finder, hyperdock for clip to windows and hover state on dock).
I’m good with most of your suggestions. I’d say some new sharing options baked into 10.9 as well (airdrop seems like a joke), and an iLife update (not really the OS, but most people think of it as part of it, since it ships with it).
iCloud improvements would be nice too. Especially if it became an easier way to share (more like dropbox).
I’d say the worst has to be that beige PowerMac POS above. The last few versions of the white iBooks really don’t hold up (I’ve seen a lot of college students with them ruined from use). Especially when they were sold as a cheaper laptop during the Aluminum MBP era. So that would be on my list too.