I don't know if you've ever seen the tiddlywiki MonkeyGSD, but I think you should look at it. It's a very simple project, but it's mature, and has a lot of functionality that you don't have. Specifically, filters for things like projects with no next action, and a tickler file.

I like this program alot, so much so that I am converting over, but I would love to see some of that functionality added in.