Taking a handful of destinations from SIN (including all of JQ, VF, 3K, MU, 9W and JL codeshares), the following destinations in Asia would be "connectable" from most SIN bound flights from Australia.
- BKK
- BOM
- CAN
- CGK (2 flights)
- DEL
- HGH
- HKT
- KUL (2 flights)
- MES
- MNL
- NRT
- PEK
- PEN
- PVG (2 flights)
- SGN
- TPE
As for connecting from Asia back to Australia, the list is the same; in fact, pretty much every destination I took in the handful can connect to the services to Australia, though in some cases you'll be waiting a
long time for the connection (viz. greater than 6-8 hours). So not ideal.
Notwithstanding that the flight which arrives in SIN the earliest to allow the greatest number of connections only operates on alternate days (and it's an ex-SYD flight), and putting aside all airlines that people may love to hate (e.g. Jetstar), on paper there are still quite a few Asian connections possible. (Naturally, for us Eastern seaboard pax, QF will most likely push us onto SYD on the days when QF81 is operating for the earliest arrival to SIN).
Day flights from SIN to Australia are obviously more comfortable, though that said there are less Asian destinations that have services that land in SIN in time to connect to day flights (e.g. leaving at around 0900 to 1000) (notwithstanding arriving in SIN at around midnight). Definitely could still work, though.
Similarly for PER, putting a flight to PER which leaves SIN in the afternoon (or early evening better) allows connections from a good handful of destinations.
To be honest, irrespective of keeping the FRA service, the "handcuffs" for flight timings are somewhat still there due to BA's SIN-LHR codeshare being proposed, plus the AY codeshare SIN-HEL. (That said, you don't
really have to worry too much about the connection times to these flights, since they are so late at night).
I should probably point out that most of my checking has assumed a MCT of 60 minutes, which means that if going from QF to Jetstar or vv., through-check is possible (as long as flights are on the same ticket). If this is not the case, or people like to leave more room for comfort, then that might be a problem.