This is wonderful!
Thank you for producing it and sharing.

I enjoyed that crash course discussion and hope lots of people find it helpful.
Each of the books has its own benefits. The Roman Missal antiphons have official English translations which are generally printed in missalettes. The Gregorian Roman Gradual has authentic music and suggestions for lectionary sensitive substitutions. OT 17 A has the suggestion of a communion antiphon on the pearl of great price (margarita in Latin) and I'm just so tempted to use it this week. I'm thinking maybe at the offertory so that I stick with the missal communion later. It would also be close to the time of the actual gospel/homily when they first hear the text.
I have been using the entrance antiphons (missal version) as verses with some Taize or other refrain since our masses resumed in June without hymnbooks. My amateur cantors have done well getting used to the new routine. It used to be my routine to sing in this way at communion time as the choir members went forward to receive (they would join in singing the refrains from the aisle amongst the congregation) but now I have switched to The Proper of the Mass by Fr Samuel Weber which I sing by myself until they return and we can switch to some other more familiar option 4 song. It's not a full choir any more either but a handful who brave the dangers and sit socially distanced in the choir area.
Another book to mention is the English version of Simple Gradual by Paul Ford called By Flowing Waters

Not that it's addressed to me, but someone asked me that before. I just stated that people tend to do that which is easiest, but for Mass, we should only do that if we are incapable of doing better.

If the Roman Missal lists options in order of preference, why is the number 1 option almost never heard, and the number 4 option almost always heard? My bishop [my pastor, the liturgy committee in my parish, x musician at some conference I attended ] doesn't see a problem with hymns and contemporary music, so why should we "turn back the clock"?

I can tell you that I mentioned this issue in a bulletin column a while back and someone was so incensed that I insinuated that doing option iv was deficient relative to option i that they sent it to the bishop and I was addressed by someone higher up the food chain as a result. Fascinating. The thought of doing chants (in english, to boot!) was so threatening to this parishioner that he couldn't address me directly but went straight to the bishop. He couldn't stomach me mentioning that hymns only loosely qualify as category iv. What's even more fascinating is I made appeals to VII documents rather than ancient ones, which, to every uninformed catholic's surprise, also calls for plainchant (lol).

I'm pleased to report that I kept my job and we are still singing antiphons. That said, my keeping my job has more to do with my priest than with myself. Deo gratias.

Chris, here’s what I would do:
Affirm their feeling and sympathize. Explain I think this is forward progress, not backward, then ask them “where do we go from here?” Doing this puts the onus on them to offer a solution while you are making clear you drew a line in the sand. Sometimes this helps. Also, i refer them to the contemporary Mass where we arent “turning back the clock”.

Oh great suggestion I’ll add that. And I’m very glad you find this useful

@lmassery Thank you for this, it came at just the right time. I typeset a score of your 17th Sunday Introit hymn this morning, printed it off, and my choir sang it for Mass this morning. I have a few points of feedback based mostly on this particular one - I haven't yet looked closely at your texts for Sundays to come.

• Commendable versification of the entrance chant! Deus in loco is one of my favourite introit texts.
• I was unsatisfied with the second verse provided. The rhyme structure did not match the first verse, and I couldn't see the rationale behind the choice of which verse from Psalm 67(68) to use. I opted to replace it with Psalm 67(68) verse 2, since verse 2 is the psalm given for this introit in the Graduale Romanum. I used the LM text by Tate & Brady found at cpdl, which has a more closely-matching rhyme scheme to the first verse.
• ...
• I thought there was an issue with the rhyme scheme in the doxology, but I must have imagined it. I tried to find a better one, but it turns out it is the one you had included already.

I set it to Winchester New, which was one of your suggestions. The choir sang in harmony for the second verse. It was very successful!

I have attached the score I made up this morning. It's on an A5 sheet, but in the end I printed it in A4.