One way to deal with re-generation is to use a cron to generate the whole thing (or just changes) every 15 minutes. Then you can tell people their changes will be live in 15 minutes.

It doesn't like ttree is a good fit for you though. Just write your own script that grabs all the content and calls TT directly. It's not hard. There's no reason to use ttree if it doesn't obviously fit your model.