Instead of firing him, Jagger/Richards kidnap him and put him in forced cold turkey, rehab, and therapy. Treatment works, and he's on the next album instead of Mick Taylor. Then what?
This is really hard to do. Brian Jones wasn't just fired because he was a problem in the studio. The Rolling Stones could and did compensate for Jones' incapacity there.
The breaking point was touring. The Stones were going to tour in North America-and Jones was in no condition to play and even if he was-he wasn't being allowed to enter the United States.
If Jagger and Richards had liked Jones more than they did-the only way Jones stays in the band is as a studio only member the way Syd Barret briefly was for Pink Floyd, or Brian Wilson for The Beach Boys.
You'd then need:
A. For Jones to actually recover in the touring interim-somehow...
B. For the touring guitarist not to be invited to take Jones' place. A real temptation for Jaggers and Richards.
Jones being "on" Let It Bleed means the album is more like Beggars Banquet-recorded essentially with Keith Richards as the sole guitarist. That impacts the sound obviously.
A scenario where Jones is not fired outright is one in which he won't be certain what his status in the band is throughout the North American tour. Under that cloud of uncertainty-he isn't going to have an easy time giving up his habits.
Even if Jones is somehow clean and sober by the time of the tour-if he can't get into the United States-his future as a member of the band is precarious.