Just an idea, you could make the behavior about warping added to every Zerg structure you want including creep tumor, since they are on creep anyway. It will be based on structures but in this way will be on creep too.
Or you could use a build ability like build zerg structures taking that one as it requires creep and making the build times 0 for the specific units you will warp and just adding a Warp In visual/actor/model whatever at the time of its placement or training.