Why did God the Father choose suffering for Christ and not the lucrative reigning power of an emperor of this world?

Can't God the Father choose Christ to come in reigning power as an emperor of the world to become a savior?

Yes HE can and will when Jesus Christ's Return and Reign

[Revelation 20:4] And I saw thrones, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God, and which had not worshipped the beast, neither his image, neither had received his mark upon their foreheads, or in their hands; and they lived and reigned with Christ a thousand years.

Why did God the Father choose suffering for Christ instead?

For our own sake, Christ needed to suffer as a sacrifice for our sins so we could be forgiven

[Hebrews 9:22] And almost all things are by the law purged with blood; and without shedding of blood is no remission.

[Hebrews 9:28] So Christ, having been offered once to bear the sins of many, will appear a second time, not to deal with sin but to save those who are eagerly waiting for him.

Jesus told us the answer when explained three things:

1. What is God's chief motivation?
2. What is the greatest expression of that motivation?
3. Who are the disciples?

First, God's chief motivation is love:

36 “Teacher, which is the greatest commandment in the Law?”

37 Jesus replied: “‘Love the Lord your God with all your heart and with all your soul and with all your mind.’[c] 38 This is the first and greatest commandment. (Matthew 22:36-37)

Second, the greatest expression of love is to lay your life down for your friends:

9 “As the Father has loved me, so have I loved you. Now remain in my love. 10 If you keep my commands, you will remain in my love, just as I have kept my Father’s commands and remain in his love. 11 I have told you this so that my joy may be in you and that your joy may be complete. 12 My command is this: Love each other as I have loved you. 13 Greater love has no one than this: to lay down one’s life for one’s friends. (John 15:9-13)

Third, Jesus declares the disciples are his friends:

14 You are my friends if you do what I command. 15 I no longer call you servants, because a servant does not know his master’s business. Instead, I have called you friends, for everything that I learned from my Father I have made known to you. 16 You did not choose me, but I chose you and appointed you so that you might go and bear fruit—fruit that will last—and so that whatever you ask in my name the Father will give you. 17 This is my command: Love each other. (John 15:14-17)

We know of soldiers, firemen, parents, and police who have laid down their life for people they loved. Are they greater than God? No! Thus if God values love and is the greatest lover in the universe and that love requires giving your life for those you love and you have picked people to call friends, you must do as Jesus did.

As for the false choice, Jesus will return to reign as emperor of the world. However, when he does, the time for mercy will have passed; he will come to judge the living and the dead. It is for the sake of sinners who need time to repent that Jesus delays his return, so that as many may be saved as possible.

However, since you are a poet, a fitting response is found in one of God's greatest poems, Job. As you read this, having heard all the things that Leviathan will NOT do for you, understand that the point of this speech is to declare what God WILL do for you!

41 “Can you pull in Leviathan with a fishhook
    or tie down its tongue with a rope?
2 Can you put a cord through its nose
    or pierce its jaw with a hook?
3 Will it keep begging you for mercy?
    Will it speak to you with gentle words?
4 Will it make an agreement with you
    for you to take it as your slave for life?
5 Can you make a pet of it like a bird
    or put it on a leash for the young women in your house?
6 Will traders barter for it?
    Will they divide it up among the merchants?
7 Can you fill its hide with harpoons
    or its head with fishing spears?
8 If you lay a hand on it,
    you will remember the struggle and never do it again!
9 Any hope of subduing it is false;
    the mere sight of it is overpowering.
10 No one is fierce enough to rouse it.
    Who then is able to stand against me?
11 Who has a claim against me that I must pay?
    Everything under heaven belongs to me.

Jesus was tied up, was pierced, does speak tenderly, does make a covenant to serve us, his garments were bartered away, and his side was thrust through with a spear. On the flip side, Leviathan represents the evil world system (and its head, Satan), an empire of force that dominates the World for evil. That is something God did not want for his Son. Leviathan will be destroyed, and its end is written of in Revelation 13. Jesus' empire will be different, because the master will be the servant of all.