This makes a lot of sense, thanks!
I'm thinking 976 becomes BPJ, Mandai, express before and after the
Zoo, covering Springleaf and Nee Soon and YCK up till the junction
at YCK Station, then going express until the bus stop just before
the CTE to provide possible transfers to 857, then express again
until Jln Kayu, then following the original route to Punggol.
859 extension to Sengkang would make sense although that'll be
pending the Sengkang expansion.
I was thinking the other way actually ... of 976 skipping
Woodlands Rd (seeing as there's 160/170/178/960/961) and go
straight to Mandai Rd, serving a number of the important stops
(i.e. some of the camps/landmarks) before Mandai Lake Rd, and at
least the one pair after that for transfer to 138. That'd provide
the link to BPJ while not compromising 927. I shall trust you on
the important YCK stops because I don't know the loading well
there. Alas.
As for 859 ... doing two loops in Sembawang just seemed
excessive, I'd narrow it down to just one at Admiralty Dr /
Sembawang Cres / Sembawang Ave before proceeding on to Yishun.
859A/B can well become a standalone feeder, and links to Yishun
near Canberra Rd are still provided by 856. (Or otherwise, an
off-peak 981 via Admiralty Link.)