Chinese gangs are behind illegal weed farms across the US

Not really? There's still going to be illegal farms in states where weed is legal as long as cultivation is as restrictive as it is (which is in large part due to lobbying from ag companies seeking to regulatory capture the industry).

There won't be under the table weed farms in residential housing (or at all) once establishing production on agricultural land at scale becomes accessible.

If recreational consumption of marijuana is legal there is absolutely no reason why cultivating it should be treated any different than tobacco (i.e. cultivation is not a crime at any volume but sales/distribution without a license likely is). And a license for sales/distribution shouldn't be a major hurdle but rather a bit of paperwork and documentation.

The only reason criminal orgs even grow weed now is because we have an artificial barrier to entry that keeps it as a profitable enterprise. Once marijuana and other crops are on the same footing, there'll be no reason why they would be cultivating it any more than why they might try to grow their own food.