John 14:10--Union Between God and Christ?

Greek (WH):  οὐ πιστεύεις ὅτι ἐγὼ ἐν τῷ πατρὶ καὶ ὁ πατὴρ ἐν ἐμοί ἐστιν; τὰ ῥήματα ἃ ἐγὼ λέγω ὑμῖν ἀπ' ἐμαυτοῦ οὐ λαλῶ· ὁ δὲ πατὴρ ἐν ἐμοὶ μένων ποιεῖ τὰ ἔργα αὐτοῦ.

According to this verse, Jesus could do powerful works because he was "in the Father" and the Father was in him. 

NWT 2013: "Do you not believe that I am in union with the Father and the Father is in union with me? The things I say to you I do not speak of my own originality, but the Father who remains in union with me is doing his works."

It is hard to explain the significance of ἐν when it comes to Johannine and Pauline writings. Is a form of mysticism suggested by such language? Even believers are said to be "in Christ" or receive the peace of God "in Christ Jesus." See Philippians 4:6-7.

Frederic Louis Godet offers one perspective on 14:10. I quote his remarks in full:

Jesus indicates to Philip two signs by which he ought to have recognized and may even at this moment recognize in Him the true appearance of God. He does not say that the Father and Himself are one and the same person. He constantly prays to the Father, saying: Thou. But it is a union by which they live the one in the other (comp. Gess), and this relation has as its background the life of the Logos. The words Believest thou not? show Philip that his prayer must be regarded as inconsistent with his faith.

There are in the union of Jesus with the Father two aspects: I in the Father: Jesus emptying Himself in order to transfer Himself to God; and the Father in me: God communicating to Jesus all His wealth of strength and wisdom. On one side, Jesus making a void in Himself; on the other, God filling this void.

After this, Jesus characterizes each of the two sides of this relation by that one of the manifestations of His life which is most fitted to bring it to light: the first by His words; the second, by His works. Not one of His words that He derives from Himself and does not receive from God! Not one of His works that is not wrought through Him by God Himself! Of His own wisdom, nothing! By the strength of God, everything. The negative clause is better suited to wisdom; the active form, to power. The following verse explains why the words are placed here before the works: comp. the reverse order in John 8:28, where Jesus is speaking to the unbelieving Jews. The first sign of the community of life and action between Jesus and God, for prepared hearts, is His teachings; for those less disposed, it is His works. We may hesitate between the readings λαλῶ and λέγω, in the first clause. In the second, the term λαλῶ, in any case, is perfectly suitable. Jesus is only the organ of the Father: God speaks; Jesus announces.

See https://www.studylight.org/commentaries/eng/gsc/john-14.html