My take is different from yours. You should not omit other GRC where there are equally capable opposition candidates. I expect Holland Bukit Timah GRC with very strong opposition team to kick out Balakrishnan. The YOG budget is Vivian own graveyard. If he think he can get credit out of YOG, he is over-estimating his credibility. Besides, he has been consistent in dressing down Singaporeans thru his parliament and other speeches - that alone spells doom for him now that the power lies squarely in the hand of those he detested.
Bishan Toa Payoh, a flow over from Potong Pasir might just bring Chiam back to parliament again. If Hougang can spill their support base to Aljunied. Same apply to potong pasir spill over to its neighbouring town.
Marine Parade and Tampines are closely watched - Tin Pei Lin and Mah Bow Tan is PAP toxics for now.
Other GRC and SMC where WP are contesting. NOw that WP has garnered popularity in Singapore, it might spill over to their support base in other constituencies like Kallang Moulmein GRC. I heard arrogant Liu Tuck Yew is not a popular candidate among the residents there.
The ideal result is that PAP may just lost half of its power in parliament. An ideal situation for Singapore and its people.