Syzygium malaccense is also native to Nth Qld. The fruit is not as great as the really good types, but the plants are probably a lot tougher. It might be possible to graft an improved fruiting type onto a tougher rootstock plant malaccense. Maybe even another closely related Syzygium.
I have grown quite a few Nth Qld Syzygium, they are mostly fairly tough outside that area. I often found growing from seed was better than trying to move seedlings south.
The choice of pot mix is also important in helping them survive winter.