Trent,
1) To clarify, the "dramatic conversion story" idea you refer to wasn't the same thing as the half way covenant. Some New England Congregationalists (not all) required a conversion story. The half-way covenant was a later development in New England (a generation later) that was actually a return back to the Presbyterian practice of allowing adult non-communicant members of the church. So they are different issues. This is a great book on the topic
https://www.goodreads.com/book/show/259820.Visible_Saints
2) It should be noted how far Riddlebarger's anti "revivalistic tendancies" go. I supported a local evangelist in Orange County for many years who dedicated his life to sharing the gospel with others (and lived an extremely frugal life with his family to be able to afford to do that full time). He was a member of Riddlebarger's church and the elders were very opposed to this man doing evangelism. It was their opinion that evangelism takes place when people are invited to church to hear a preacher from the pulpit. It's not directly the same issue, but it is related. I would take Riddlebarger's comments with a few spoonfuls of salt.
On a related note, I recommend reading
Jonathan Edwards and The New Side/Old Side Presbyterian Schism https://sacrosanctgospel.files.word...than-edwards-old-side_new-side-final-copy.pdf
3) "in many places this seems to be the blueprint." Can you clarify what you are referring to? Your personal experience in 1689 churches, or what?
4) Make sure to review the books of church order for various Presbyterian denominations to see how they handle the question of admitting someone to communicant membership. Excerpts can be found here
https://contrast2.wordpress.com/2019/04/11/do-presbyterians-have-regeneration-goggles/ For example, the OPC BCO IV.A.3 states
That sounds similar to the 1689 churches I have been a part of. One church asked candidates for membership to write a brief testimony that would incidate the above (i.e. awareness of their sin and their reliance on the merits of Christ alone). That would be published in the bulletin for several weeks prior to the vote to admit them to membership, giving the members time to address any concerns. I don't recall anyone ever being denied membership for lack of a sufficient testimony.