I'll butt my head in here:
Christ is Mediatorial King, sovereign over all right now. Further, I agree with those who've talked about the use of general equity (the Presbyterians at least). But I have no resources to help you but the book Messiah the Prince by William Symington (for the topic of Christ being King over all (see the book of Daniel)). This then has profound impact on one's view of the law, the Kingdom, and eschatology.
Eph 1:19 ...according to the working of his great might Eph 1:20 that he worked in Christ when he raised him from the dead and seated him at his right hand in the heavenly places, Eph 1:21 far above all rule and authority and power and dominion, and above every name that is named, not only in this age but also in the one to come. Eph 1:22 And he put all things under his feet and gave him as head over all things to the church, Eph 1:23 which is his body, the fullness of him who fills all in all.
Mat 28:18 And Jesus came and said to them, “All authority in heaven and on earth has been given to me. Mat 28:19 Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, Mat 28:20 teaching them to observe all that I have commanded you. And behold, I am with you always, to the end of the age.”
Psa 2:2 The kings of the earth set themselves, and the rulers take counsel together, against the LORD and against his Anointed...Psa 2:7 I will tell of the decree: The LORD said to me, “You are my Son; today I have begotten you. Psa 2:8 Ask of me, and I will make the nations your heritage, and the ends of the earth your possession. Psa 2:9 You shall break them with a rod of iron and dash them in pieces like a potter's vessel.” Psa 2:10 Now therefore, O kings, be wise; be warned, O rulers of the earth. Psa 2:11 Serve the LORD with fear, and rejoice with trembling. Psa 2:12 Kiss the Son, lest he be angry, and you perish in the way, for his wrath is quickly kindled. Blessed are all who take refuge in him.