The best I have come up so far is two trips and around 3100€

1. trip
NUE-IST-BEY (322€) TK economy (Asia ✅)
BEY-IST-CAI (403€) TK economy (Africa ✅)
CAI-IST-SYD (536€) TK economy (Oceania ✅) - or 1437€ TK business
positioning SYD-CGK (Flying Blue business award - 30.000 miles + 100€)
CGK-IST-EWR (629€) TK economy (North America ✅) or 1800€ TK business
JFK-FRA-NUE (326€) Lufthansa (getting-home-flight)

2. trip
NUE-IST-BOG (779€) TK economy roundtrip (South America ✅)
BOG-IST-NUE (Europe ✅)
alternative VNO-IST-BOG roundtrip in business for 1890€ with Ryanair feeders to VNO

wouldn't like to stick too much in economy class - so if I took the bait I would buy the business class oneway from CAI to SYD and would use my last E+ voucher for CGK-IST-JFK and 2 LH evouchers to upgrade the JFK-FRA flight. then the trip would be comfortable at least.