Though 252 goes up to Joo Koon, there's still 50% chance that
it'll remain unchanged to cater its usual pax, unless terminal
location does not cause much omission of sector travelled in the
event of terminating.
Trunk wise 185 is hot fav. 
180 also can pull in. But other existing
BNL services is questionable, since those long haul like 30 is too
long to extend further west while cutting 182,192 to joo koon
& tuas is like "locking" them to west, reduce contact area and
transfer points available
maybe a trunk service can merge with 252 and extend to boon lay...
maybe 198?