The only way the catch, weigh and release will ever work is if you have a dedicated boat marshal with a provided scale that was calibrated to match every one scale in use. A way to video yourself weighing fish in plain sight might work, but again, who is providing that gear or will it just be a requirement on the angler to provide that before they can fish? Let's face it, a lot of guys who fish are doing good to use their cell phone, much less keep a camera rolling, swap chips, make sure the batteries stay fresh, etc.
Only the big leagues have enough money and man power to make that happen. I'm not sure you'll ever be able to make it happen on the lower level tournaments. Relying on anglers to weigh and keep track of their own fish when there are thousands of $$$ will only lead to cheating.