I think it would be bad you could get some hq slow growing crops from WWW so there wouldn't be point in growing them which would be stupid.
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Then you should also increase the quality gain on slow growing crops so they have reasonable quality, instead of -1/+5, make it -1/+20 for grapes, hops, pumps
In Legacy it worked this way. I remember being part of group and our leader bought really high quality herb table that turned WWWs into seeds that were above any of our farming.