I see a new product-hunt alternative launched every couple months here. Maybe I’m cynical, but I don’t think we’re going to displace product hunt with things like new voting dynamics. They already have the network effects, so I think you’d need to make a relatively large change to stand a real chance.

Edit: Here’s a proposal for a bigger change. do some free advertising for the submitted ideas. Run simple Google/youtube/facebook ads for them, just directing people to their page on your platform. Hopefully this doesn’t burn too much cash, since you’re actually advertising for their page on your platform, so it’s good for you in the end. Perhaps submissions have a small fee in the long-term, to monetize the platform.