Helo,
Of course it's possible to hack MediaWiki further more. But I believe it's far easier to install a blog software, have it ready and set up in like 10 minutes.
The aim of the blog will not aim at building a cooperative content, that's what wiki is for. Instead it will help easily publish important messages from the dev/admin team to the userbase be it maintenance, new releases, ongoing changes available on test.wikipedia.org .
In other words, just because you have a hammer, that doesn't make everything a nail.