MadScientist,

I am very grateful for your input on this thread !

I can see that cutting off every other engagement tooth on the slider mechanism would double the time window for the shift engagement.
It seems it would not affect the synchro - gear cone holding ability. Then once the slider is on the gear, you are IN GEAR.
If the slight back angle is present on the teeth then it will stay IN GEAR, even on decel.

Is there a strength or longevity decrease on the engagement mechanism ?

Even f you disengage the clutch properly during the shift, you now have half the tooth area to perform the engagement.
There is always some "slamming" involved in this process.

Too bad they don't make slider components with, say, 1.5 times the tooth spacing but 1.5 times bigger teeth.