>Another thought for running from cab cars: in addition to the control wiring issue, with the locomotive pushing, wouldn't you get noticeable slack action just switching to dynamic without some braking throughout the train?

Rearranging the slack is also a concern when the locomotive is leading.

>Going from fully bunched (pushing) to fully stretched (braking)? Always having blended braking should help with that.

Blended is no guarantee against slack action either because I know a lot of "engineers" who regularly get slack, sometimes severely, in a four car passenger train when switching from power to blended braking.