Paidion, sorry so slow to reply....
You wrote:There is no uniformity of doctrine among Pentecostals.
There is one thing and one thing only which is in common among all Pentecostals, and that is the belief that a "baptism in the Holy Spirit" should follow the "conversion" experience.
There are Catholics, Protestants, Reformed, Baptists, Lutherans and Methodists who are Pentecostals.
People in mainline (or more traditional) denominations who believe in speaking in tongues are "charismatics." They stay within their denominations and still believe in their other (non-Pentecostal) doctrines: They don't leave and become Pentecostals.
Afaik, all Pentecostal denominations are (uniformly) premillennial & dispensational. The Vineyard denomination came into existence during the "charismatic movement" and might be considered Pentecostal in an indirect sense. They probably identify themselves more with being from the charismatic movement than classical Pentecostalism. Also, Vineyard is Calvinistic and I know of no Pentecostal denomination that is: All Pentecostals are (uniformly) Arminian, afaik.....
You also wrote:There are Trinitarians, Binitarians, Unitarians, and Modalists, who are Pentecostals.
I've not heard of a binitarian Pentecostal denomination. Can you tell me one?
You also wrote:There are Pre-tribbers, Post-tribbers, and Mid-tribbers who are Pentecostals.
There are Premillenialists, Postmillenialists, and Amillenialists who are Pentecostals.
Pre-Mid-Post-tribbers are almost always dispensational, though some postmillennialists and amillennialists also believe there will be a future "great tribulation."
I don't know of any Pentecostal denominations that
aren't premillennial (and have looked for a long time).
I've also never heard of a postmillennial or amillennial Pentecostal denomination. If you know of an Amill one, please let me know which one it is...I want to check them out (I had to leave an A/G Bible college and the A/G over this issue, becoming and amillennialist while at the college).....
Lastly, you wrote:Pentecostalism seems to trancend all doctrinal positions.
Pentecostals are, for the most part, "orthodox" (with exceptions like the "oneness" Apostolic denominations). They are all premillennial and dispensationalist...as far as I know.
At one time I would have "jumped" at the chance to go to an Amill Pentecostal denomination. These days I do not know if I still believe tongues is the "initial physical evidence" as (my former) A/G denomination does.
I'm thinking you must have an amillennial Pentecostal denomination up in Canada(?). I know of none down here or any place else.
Thanks,
Rick