I'll admit, it was a little difficult to follow with all you parentheses, but I'll give it a stab. Heres what you need to know. I know this from a good bit of experience with mites, not necessarily on phals but real mite factories like english ivy, palms, and crotons:

Mites thrive best in hot, dry/non-humid conditions, i.e. think desert conditions, or winter indoors with forced heating. Its not so much a function of light as it is temperature (ignoring for the moment that more often than not, increasing light will increase temperatures). Keeping them on the cool humid side will help, but it will only suppress mite populations, not necessarily eradicate them. Keep in mind to that phals love it warm, so if manipulating temps/humidity to suppress mite population you sacrifice decent plant growth. Treatment with oils and/or soaps alone or in conjunction with cool/humid treatment should help eliminate the problem. Theres not much else aside from oils and soaps, at least that I'm aware, that 7is organic that can be used to kill mites. Mites are one of the hardest things to control and get rid of because regular pesticides don't work on them. There are skull and cross bones stuff out there for them. Kelthane, Avid, Azatin come to mind. YOu can find kelthane in a few places, but I THINK you need an applicators license for the latter.

As far as prevention, there are steps you can take and most of them are the same as for growing in the home. But nothing is foolproof. And when you have plants that are susceptible to a certain pest all gathered together in one place, its most likely only a matter of time. Some common sense treatment/prevention tips:

1. Isolate new plants that come in and give them several pesticide treatments (organic or otherwise) before joining them with the rest of your greenhouse population.
2. Make the environment as inhospitable as possible for the pest.
3. Treat tools between each plant.
4. regular scouting to catch problems early.
5. Preventative spraying, which is something most production greenhouses do.
6. This is something you can do in a greenhouse that isn't really practicle in a home environment: beneficial insect release. There are predatory mites that prey on your pest. But you have to know what kind of mite you have because some of the predatory mites can be species specific.

All in all, I think simply treating with oil or a soap should be all you need. Phals, at least in my experience (YMMV!!!) aren't that susceptible to mites. And in my own personal experience, if a plant gets a pest its usually moderately resistant to, eradication is relatively easy. Unlike habitual mite factories, where you may be spraying the plant as long as you have it no matter what you do.

I make it a practice to wash the plants down early in the am . when Temps. are high and humidity is low , mite season , also spray them with Safers covering the upper surface and under surface of the leaf weekly. My daughter had trouble with them .Using the Safers soap every 3 days for 3 weeks got rid of them, washing the leaves before treating, let dry treat . Neem kills them but is a problem if you have high light . Keltane if plants are outside but take safety measures when using . Gin

Last fall my little Equestris was infested-this was the first time I ever had mites. The only thing I had on hand was Schultz houseplant and garden spray.It does list mites on the label. I took the plant out of the pot, soaked every part of it with the bug spray including roots and crown and let it sit for an hour or so. I then rinsed the plant off, bleached the pot and repotted in fresh mix. Happy to say my little plant is now blooming and the mites never spread anywhere else. I think the key is getting rid of all the critters the first time around.