I love how so many 'weeds' are beneficial herbs! My yard has dandelions, plantain, yarrow, violets, and then the food items that are also known as beneficial, like alfalfa, comfrey, nettles, and kale. I need to move some thyme, oregano, echinacea, so much stuff into their yard. It is large but not as diverse as it could be.
There is an herb site that has a good variety of seeds and plants,
Steictly Medicinals, used to be Horizon Herbs, in Oregon.
One plant I got from them was Gynostemma pentaphyllum, aka jiao gu lan. It is a sweet tasting member of the cucumber family that so far is hardy in my unheated greenhose in zone 5, it is vining and roots readily as it covers ground. It is looked at as a ginseng type plant, known for longevity. Anyway, had some that I gave them and they went crazy for it.
I have found the 'Kapoor'type of tulsi basil to reseed readily, it is known as an immune modulator, good for general health.
A plug for two pf my favorites, allheal, aka prunella Vulgaris, that is a super easyground cover, a member of the mint family, it has antiviral properties against herpes viruses in humans, so am thinking that it might be good for chicken herpes diseases like Marek's and fowl pox. Lemon balm does too.
And also blackseed, an easy annual flower, looks like Love in a Mist, but is a different species, nigella sativa. It is huge in the Middle East, edible, has studies on poultry showing a reduction in influenza I believe.
So many directions wih this idea!