Assume we extend Balogun. The we have the following three with question marks over availability:
Balogun
Souttar
Helander
That's in addition to another three options.
Bassey
King
Katic
If we keep Bassey he should be clear first choice left back. King should only feature in a few matches unless we have an injury crisis. Katic is likely out of the picture, as you say, and we definitely need better than him.
I say that we should focus on getting another central defender who can be relied on and is also an improvement on Balogun.
If we keep Balogun then I suspect that it is because we have no other options.