In class recently, we started discussion on the doctrine of anthropology (man). I noted that before sin and salvation became an issue, man was tasked to fill, rule, and subdue the earth for God's glory (Gen. 1:26-28). Thus, a successful kingdom rule over the earth by man as mediator is foundational to God's purposes. This is a good clue that a kingdom rule over creation is the primary thing God is pursuing.
Redemption of people is a big and wonderful theme in Scripture, but it fits under God's kingdom purposes. Redemption/salvation is not an end in itself. It is a means in God's purposes for both relationship (with God and people) and function (rule and subdue the earth).
For a theological system to be comprehensive it must do more than address salvation, as important as that is. It must adequately account for the 'kingdom over the earth' theme in Scripture.