I actually think the Q111/Q113s short turning @ Jamaica Ctr is a great idea!
Now about the other one..
I don't think the Q42 should be extended..
The Q42 doesn't run enough nor have enough ridership (IMO) to warrant an extension. (I didn't 100% agree with all day service returning on the route in the first place..)
I always see Q42s come into Jamaica Ctr not even SRO (same as exiting Jamaica Ctr)... The buses most likely would run up to Sutphin empty.. which isn't very cost efficient...
I don't think the Q84 should be extended either for the ridership issue either.. (That route does get riders in the rush hours, but outside of those times, the route itself is not even SRO, everytime I've ridden it, or seen it on Merrick, it was practically empty...)
As for the Q83,The Q83s will come into Jamaica Ctr even more packed than they are now.. BUT the route does have the frequencies to support this (IMO). It is better to extend a higher ridership route, than a lower ridership route (again, IMO)
If a route HAD to be extended to Sutphin on the (which I don't think is a high enough ridership subway station, nor a high trafficking terminal in the first place...) it would have to be a high ridership route, like the Q5, Q85, Q83 or Q4.
A good example to support this, the Q40 (which terminates at Sutphin on the F).
I've seen this route numerous times and have observed the ridership patterns, not as many people get on at Sutphin/Hillside, as compared to Sutphin/Archer.. mainly because Sutphin/Archer is a higher ridership/trafficking station...