Profit-Sharing in Reward Campaigns: Legal & Financial Traps?

Hey everyone, I'm a gaffer usually dealing with things like setting up an Orbiter or rigging an LS 600d Pro for a V-RAPTOR XL shoot, but I’ve got a question outside my usual realm. My buddy and I are looking into a reward-based crowdfunding campaign for a short film concept, think sci-fi, a bit ambitious, but visually stunning. We’ve been discussing offering a percentage of any future profits to backers as a higher-tier reward, on top of things like signed posters or special thanks. We've seen other projects try this, so we thought about it. But we don't have a formal securities structure set up. Are we opening ourselves up to major legal headaches or financial traps by promising something like that without a clear, established system? I’m genuinely asking because we want to do this right, but also want to offer enticing rewards. What are the big pitfalls here?