You say WA is lax in its rules and has no enforcement. How would this change the enforcement? The recreational mining rules have been in the legislature since sometime in the 90s. That would be a decade or more in which to collect information on the what, where, good, bad.
This is one of a whole lot of activities that need an honest look at the impacts to fish.
A question that has been asked by miners "why should I be restricted from killing or injuring fish because of my recreational choice while you (F&G agencies) license people to kill those same fish commercially and recreationally." The fish is just as dead.
1. The money collected from issuing mining permits/licenses would go to enforcement, at least in part. That isn't happening now.
2. WDFW simply has not collected data on the effects of suction-dredge mining: it just has not been a priority. I suspect that's due to lack of funding. Money from the permitting/licensing of stream mining could support a genuine data-collection effort.
3. On the Olympic Peninsula, where I fish, one wild winter steelhead can be kept during the season. (Some people don't keep any natives on the OP.) And fishing for winter steelhead on the Puget Sound rivers has often just been shut down completely in recent years. The concern with laxly regulated suction-dredge mining in Washington is with stream-spawned wild salmon and steelhead, for which catch limits have been more and more restrictive. So why should miners get what amounts to a free pass to do whatever they like to streambeds used for spawning by wild fish? It defies common sense when many stocks of salmon and steelhead in this state are endangered.