Sadly, I fear legislators won't do that until there's an economic advantage for their supporters. So they need some magnates to be convinced, and buy up the production before they go ahead.
Why would legislators make regulations that just save the planet but don't make them rich? /s
There are ways to mitigate unintended side effects. Start with a small small number of farms, AB test with no seaweed, small amounts of seaweed, medium amounts of seaweed, large amounts of seaweed, also AB test on which Farmers know which sample they are getting, iterate next year on results with larger number of Farmers. Buy insurance to compensate Farmers if the seaweed kills them. Discover why they died. Iterate with solution (if possible) or cancel (if seaweed always results in eventual death). Continue to keep large population of seaweed free cattle to mitigate possibly of extinction via unexpected long term consequences of seaweed.
