Not really an itinerary as such, but a bit of brainstorming...
In SIN, we'll arrive in T2, and assuming all goes well, we'll be having lunch at the staff canteen in T2. So it might makes sense if we hit the MH lounge first, for a short stay. It's a really small lounge, with minimal catering. The only redeeming feature is the set of 2 massage chairs. Then, we can proceed to T1. Skyview is quite close the skytrain, so we can drop by there, before finally heading over to the QF lounge. The QF lounge would be where we would want to have dinner. We shouldn't have any issues with opening hours either, with the QF lounge opening at 2.30pm although for those who want to drop by the EK lounge, I don't think it's open during the late afternoon.
And for KUL, the flight to SIN usually departs from the main terminal, so we'll need to backtrack from the lounges in the satellite... so I guess we'll just wing it.