Thunderroad

This all sounds good to me, including the Australia/New Zealand option. (IMHO, New Zealand is the most beautiful country in the world and Sydney one of the most spectacular cities.) As you've already noted, you're interested in the 380 suites. I'd maximize that to the extent possible, as it really is a special experience (not that "ordinary" SQ F is anything to sneeze at).

One other thing I'd mention is to try to arrange your schedule to get at least one long transit through SIN. The airport itself is probably the easiest and most enjoyable big airport in the world to transit through, with lots of special features, most notably its butterfly garden. The SQ Private Room, a lounge within a lounge within a lounge, is very nice. And if your transit is quite long, the airport hotels within the airport are very decent places to park yourself.

This probably doesn't fit within your parameters of using your miles to fly SQ in style, but if you have enough miles and time you could fly to or from South Africa from SIN in J (try to get one of the two "bulkhead" rows for the roomier seats) and break up your JFK-FRA-SIN (or vice versa) trip by flying from Europe to South Africa on LH or preferably (for the better J seats) South African Air. I recommend it because Capetown and the Western Cape region there are so spectacular (as are, I've heard, the national parks with wildlife closer to JNB) if you go the right time of year. But again, it takes you out of your way and you'd have to put some time into South Africa to really appreciate it.

Oh, and if you do intend to stop off in any place for a considerable place of time, try to take likely weather into account in planning the trip.

Hope it all works out!