Great, detailed post by fdr there. Hopefully, we can put to bed all the claims that the 737 is inherently "unstable."
On the issue of MCAS activation during TCAS, GPWS, and windshear events, a few more thoughts.
First, all of these maneuvers are hand-flown. Not only are they hand-flown, but they are dynamic situations in which there are significant changes in thrust and airspeed. As such, the pilot should be trimming constantly through the maneuver using the yoke trim switch. As we know, the yoke trim switch will always override MCAS. If the pilot doesn't know how to properly fly and trim, then that is a training issue, not a design issue.
Second, properly flown a TCAS maneuver should never enter stick shaker region. Windshear and GPWS maneuvers may be in and out of the stick shaker, but they should not be flown with a continuous stick shaker because you certainly don't want to stall the aircraft during the recovery. MCAS has some threshold values in terms of both AOA and time to trigger activation, so it is unclear whether MCAS will even activate if you are only triggering the stick shaker intermittently.
Third, I think there is too much focus on what happens when MCAS activates at a time when it is not needed as it did with the accident aircraft. Outside of the high AOA regions, the MCAS input will increase control force gradient above what would be normally expected/wanted. Approaching the high AOA region for which it was designed, the MCAS input will attempt to maintain the control force gradient as it offsets the extra lift generated by the engine nacelles. In other words, the controls should feel something close to normal when MCAS works as designed.
Finally, the aircraft is not flown with trim, nor does MCAS override the pilot's ability to trim. In the case of any hand-flown maneuver the pilot should use the primary flight controls to set the aircraft attitude, set the thrust to the desired power setting (full thrust in case of windshear or GPWS warning) and then trim accordingly to relieve control pressures. I say again, the pilot should establish the desired attitude and power setting and then trim accordingly! If the new and improved MCAS was making a trim input that the pilot did not want, that pilot could easily override it. Any consideration into aircraft design will assume that the pilot will employ standard hand-flying procedures.