Units isn’t really the point of competing in these kinds of competitions, though (or, it shouldn’t be). It’s about being inspired to create, enjoying the things others create, and being able to show off the cool things you’ve created. The monetary reward is just an added bonus for those who are particularly outstanding. Only three people get any prize money at all, after all. You can’t reasonably expect to win, but you can expect to have people take a look at whatever sweet build you’ve made.
That said, having more time to build would be very nice. To shamelessly plug the TrackMania Monthly Track Contest, we like to give builders an entire month to build their creations. This is usually more than enough time to get a solid map made, and also allows for exceptional levels of polish if the builder desires. One week can go by pretty fast, and there’s no guarantees that players who want to compete will have the time to do so. I’d recommend extending the build timeframe (if not now, then in the future).