Just a suggestion (refer to my post above).
123 (Bt Merah - Tomlinson Rd) via ex-service 605 route to Tiong
Bahru Rd, then current service 123 route to Orchard Blvd, then
Tomlinson Rd and return.
The sector between Bt Merah and Orchard via Queensway and Holland
Rd can be replaced by another service, perhaps 36?