The above discussion contains some good ideas, so I want to inform the tech team of the ongoing exchange of ideas. I think @Machina and @Ryuu96 are the ones organizing the feature wishlist for the site (sorry to ping you two if I remembered wrong and you weren't the ones).
I want to add some thoughts.
1.) Splitting the whole pot among the winners can be gamed, as people might create new users just to improve the pot by betting their signup bonus in these bets. Also I don't think the devs have the problem if bets generate more VG$ over time, but if users can game the system to gain a lot VG$ in a short time.
2.) I like @Bofferbrauer2 idea of making regular bet threads a site thing, like poll of the week. @dmillos does great work in presenting regularly interesting bet challenges and present it on the front page might help to popularize this feature.
3.) Discouraging large bets is somehow implemented already. I think the current limit is VG$1000. This may be a large sum for some users and a small one for prediction league participants or regular GameDB-updaters. I currently own VG$8,800, which allows me to place big bets if I want. But it might be interesting to have a bet maximum that moves between 10 and 1000 as 10% of the VG$ the user owns overall. That way I currently could only bet VG$880. And users couldn't bankrupt themselfs in one bet except they are already basically bankrupt.
4.) Rewards based on probability is probably difficult to create. Because the actual probability is hard to guess. But I think the reward percentage could change between bets with 2 options and bets with 10 options (and scaling in between). With 10 options you have a much higher chance to pick a bad choice.
5.) I love the idea of showing a countdown how long the bet is still open. Maybe even implement a subsite that shows all open bet threads with the ones closest to end at the top.
6.) Similarly I like the idea of a leaderboard showing the most successful recent betters, similarly to the leaderboard of the prediction league.
7.) And I love the idea to creating betting badges. The badges in detail partly rely on other changes (won double the amount would need a change of the system first).
