There were a number of in-between compromises available all along. One might have been for Jack to get a divorce, get a job in Casper (about 125 miles from Riverton) and let Ennis know he was available. Ennis would have resisted at first, but IMO they would have ended up spending an average of a week a month together; no way Ennis could resist Jack just a two-hours drive away in an anonymous big (to him!) city for long.
I never thought of something like this. I wish it could have happened. It really would've been good problem solving on Jack's part. No 'all or nothing'. Still, maybe it falls under the rough category of hindsight being 20/20?
I love the idea, though. I want to see a fanfic about this!