In future, can you please provide links and references if you want an answer? Also, when the site is somewhat busy, I don’t necessarily read every post, so use @sujato if you want to catch me!
I’m not aware of the phrase ariyo maggo, certainly it is not common. The normal phrase is ariyo aṭṭhaṅgiko maggo. In this case, it’s a little too long to compound the words together nicely, so they are separated, and declined in agreement. It doesn’t affect the meaning; it’s just stylistic. Ariyaṭṭhaṅgikamaggo would be equivalent, if it occurred.
No. Wikipedia articles on Buddhism are unreliable, and Williams is not a good scholar, best ignore him.
The Pali makes a clear distinction between contexts where ariya is used. It is used as both a substantive (“noble one(s)”) and an adjective (“noble”).
In cases like ariyasacca or ariyo aṭṭhaṅgiko maggo it is declined in agreement with the term it qualifies, and thus should be translated as “noble truth”, etc.
In other contexts, such as the very common ariyassa vinaye (misquoted in Wikipedia), ariya is declined in the genitive; the phrase should be translated “in the training of the noble”. Here, the singular can be read as referring to the noble (ones) as a group. But more likely, since it is the Buddha’s training, it refers to the Buddha specifically, thus “in the training of the noble one”. However, either interpretation is grammatically sound.
This is a very common idiom. We can confidently conclude that if the Buddha wanted to say ariyassa aṭṭhaṅgiko maggo (the eightfold path of the noble), he would have.
In the jhana formula, ariyā is a nominative plural, i.e. the subjects of the verb, and is translated “the noble ones declare …”.
Remember, the lifeblood of academics is publication. And you don’t get published by saying, “previous scholars were right”. You have to make some new contribution, or at least make it sound as if you do. So, unfortunately, most cases where Buddhist scholars make claims about new or corrected interpretations are just a waste of time.
In its typical style, Wikipedia says:
An alternate rendering of ariyo aṭṭhaṅgiko maggo is “eightfold path of the noble ones”,[5][14][15]
It sounds nice and neutral, and it has three solid references to back it up, so it seems authoritative. Unfortunately, one of these is a text on Japanese Buddhism, one is on Tibetan Buddhism, the other is an encyclopedia article. Although I don’t have access to the sources, it seems safe to assume that none of them are actually based on a knowledge of the Pali, which is, of course, the language of the term under consideration.
In any case, the grammar of the phrase does not support this translation. It certainly is an “alternate” rendering. It’s also an incorrect one.