941,945,947 & 990 should be renumbered as 341,345,347 &
409.
Would have liked 941, 945, 947 & 990 to change numbers as
well, but LTA's reply was something along the lines of commuters
having gotten used to the numbers ... or rather they don't want to
make unnecessary changes to the bus stop pole tags / info stickers
/ online e-guides etc...
Numbers that have not been taken up so far
1:Would be good if start from West since 5 & 7 are inside Bt
Merah and Clementi package.
44:Would prefer if Tampines package usage to start from CBP
since they have 47.
71:Prefer either YCK or Tampines/Clementi/CCK-BPJ package
usage.
104:Prefer Hougang-Sengkang/Clementi/Bulim use.
114:Prefer Clementi/Hougang-Sengkang.
126:Either Bt Merah or at least Tampines.
137:Prefer Sgn-Eunos or at least Hougang-Sengkang
144,146,148,149:Prefer Bidadari usage.
152,164,202,203,204,205,206,207,208,209.
I wouldn't mind 1 being an eastern service as long as it serves
the CBD. Can come in the form of, say, a split-up of 67. Otherwise
there's the feeling of being "less important" than 2. 
If 51 somehow gets split too, the eastern half can number as
152.
Also time to open up the 400s for new services. TT can utilize
them in BB / JE / Tengah etc.