I think it really depends on the dogs you already have.
I think in your case Elisabeth, a male would work better because Zefra is dominant.
For my situation, there is no way I could add any more to my pack without it upsetting the dynamics. I would love to foster, but can't with the current dogs I have.
Some dogs just go with the flow of in and out revolving door visitor canines, I wish I had that with my dogs! I give credit to the people who constantly foster and have dogs that just get along