Interesting interpretation Teresias, but going against the writer's own exposition. He would have said "king," but instead he mentions "kingdom" (see all versions and translations). I view the prophecy of Daniel as a unit, thus preferring the traditional explanation of Babylon, Medo-Persia, Greece, and Rome, especially in the light of the four beasts of Dan. 7:
38b Wherever they live, he has made you ruler over them all. You are that head of gold.
39 "After you, another kingdom will arise, inferior to yours. Next, a third kingdom, one of bronze, will rule over the whole earth.
40 Finally, there will be a fourth kingdom, strong as iron--for iron breaks and smashes everything--and as iron breaks things to pieces, so it will crush and break all the others.
41 Just as you saw that the feet and toes were partly of baked clay and partly of iron, so this will be a divided kingdom; yet it will have some of the strength of iron in it, even as you saw iron mixed with clay.
42 As the toes were partly iron and partly clay, so this kingdom will be partly strong and partly brittle.
43 And just as you saw the iron mixed with baked clay, so the people will be a mixture and will not remain united, any more than iron mixes with clay.
(Dan 2:38-43 TNIV)
Coming back to the date of authorship, it seems to be moving back in time, according to the latest research. Three examples come to mind:
1) It is certainly possible that Daniel is the author of the book (Ant. 10:267), which would put the date of the book somewhere in the latter half of the sixth century B.C. [Footnote 1: On purely linguistic grounds, the similarity of the book’s Aramaic with that of Egyptian Aramaic texts from the fifth century B.C. makes a date in the latter part of the sixth century B.C. at least remotely possible.][1]
2) John J. Collins, a staunch defender of a late date Daniel, makes an unusual concession. While acknowledging that a “precise dating on linguistic grounds is not possible,” he concludes that the Aramaic of Daniel is later than that of the Samaria papyri (Wadi Daliyeh, fourth century BCE) but earlier than that of the Genesis Apocryphon (1Q20).[2]
3) The form of the prophecies of Dan. 8:23-25 and 11 is best explained if they originated in the Babylonian Dispersion and the author was well acquainted with the Babylonian omen literature, someone skilled in the language and letters of the Chaldeans, as the account in Dan. 1 indicates.[3]
[1] Michael B. Shepherd, Daniel in the Context of the Hebrew Bible (Studies in Biblical Literature, vol. 123), Peter Lang Publishing, New York 2009, pp. 65, 66.
[2] John J. Collins, A Commentary on the Book of Daniel, Hermeneia-series, pp. 16 [footnote 156], 17, and R. J. Korner, “The “Exilic” Prophecy of Daniel 7: Does It Reflect Late Pre-Maccabean or Early Hellenistic Historiography?” in Prophets, Prophecy, and Ancient Israelite Historiography [ed. M. J. Boda and L. M. Wray Beal; Leiden: Brill, 2013], p. 348.
[3] E. C. Lucas, “Daniel: Resolving the Enigma,” Vetus Testamentum, Vol. 50, Fasc. 1 (Jan., 2000), pp. 72-76.