The thing is, the only thing that would do is make it so in the last 30 seconds of a round there is a spam of deposits and only one wins. It wouldn't increase the activity overall, just the activity at the last, and I mean very last, seconds of the week. I could consider it if people really wanted it. Let me know by replying to this post if you want it or not.
Maybe you could do a 200% bonus to the last deposit for each day? Although that the activity is still increased "at the last, and I mean very last, seconds of the" day, it would increase the overall activity throughout the week.
Just my suggestion.