What prompted Yosef to advise Pharaoh to appoint a viceroy?
Ramban: He did so in anticipation that Pharaoh would choose him. 1
Seforno, Kol Eliyahu: Since that was the objective of the dream. Also, he wanted to save Pharaoh from sinning by failing to carry out Hashem's plans.
Oznayim la'Torah: Yosef not only knew that Hashem does not punish without good reason, but he knew exactly what Egypt's sin was. As the Torah clearly indicates in Vayikra, when it precedes the Arayos with "ke'Ma'aseh Eretz Mitzrayim Lo Sa'asu" (Vayikra 18:3). Moreover, he had seen first-hand how his master had initially purchased him for immoral purposes, and how his mistress had confronted him with "Shichvah Imi!" 2 That is why he added the word "v'Atah" which has connotations of Teshuvah, and that why, once he became viceroy, he commanded all the Egyptians to circumcise. 3
Ohr ha'Chayim: Hashem informed Pharaoh in order that he appoint overseers. Also, the lean cows swallowed the fat cows to teach that in the famine that they will be fed from the years of plenty. 4
Ha'amek Davar: He was speaking with Ru'ach ha'Kodesh.
Ramban: As the Pasuk says in Koheles (2:14) "For a wise man's eyes are in his head" (he anticipates the outcome of the current situation and acts accordingly).
See Rashi to 41:45; see 39:7. Oznayim la'Torah - Bear in mind that the punishment for promiscuity is poverty (Sotah 4b, based on Mishlei 6:26).
See Oznayim la'Torah who elaborates further.
Compare to Gur Aryeh (to 41:4) - Pharaoh was likely to ask why it was he that was shown the dream, and none other. Yosef therefore concluded his interpretation, that it was up to Pharaoh to see to it, that grain would be gathered during the years of plenty. Also refer to 41:8:4.1:2*.
What are the ramifications of "Ish Navon v'Chacham"?
Ramban: He needed to be a Navon (a man of understanding) in order to provide the nation with bread according to the size of their families, exactly as per their needs, and to save the remainder to sell to the people of other nations, to enrich Pharaoh. And he needed to be a Chacham to know how to preserve the produce, to prevent it from rotting. 1
Seforno: To know what needed to be done and to put it into practice, to keep an eye on things to prevent any financial loss to the king.
Rashbam (to 41:39): Someone who understands the future and who is able to foresee the results of actions (both his own and those of others), and who possesses accumulated wisdom borne of experience.
Ohr ha'Chayim: Navon is one who knows how to store grain to prevent rotting. He must be a Chacham in geometry, engineering and numbers.
Malbim: There are two opinions. Some say that a country should have different ministers for different matters, e.g. taxes, storehouses and expenses. Some say that there should be one person over everything. Yosef said both - one Chacham should be over everything, but with people under him for various matters
See Rashi to 41:48.
Why did Yosef say, "Yere Pharaoh Ish Navon" (Pharaoh should see), and not 'Pharaoh should seek'?
Moshav Zekenim: Pharaoh should see [a clever man] among those standing here. Had he said 'Pharaoh should seek,' he might pick someone else. Also, all the Chachamim [who tried interpreting the dream] were there. He would not find a greater Chacham elsewhere.
Why does it say here "Navon v'Chacham," while in Devarim it says "Chacham v'Navon" (Devarim 4:6)?
Ha'amek Davar: There are two aspects of being a Chacham; (a) He knows many things, like it says in Avos (4:1) "one who learns from all people." (b) Intellect and skill, like it says in Mishlei, "Reishis Chochmah, Keneh Chochmah; uv'Chol Kinyancha Keneh Vinah" (Mishlei 4:7) - First acquire intellect and Charitzus, i.e. much knowledge, and afterwards toil (to understand a matter amidst another) to acquire Binah. In Devarim, it says that Yisrael has much knowledge, and is Navon (knows when to show it). Here, Navon is to influence the spirit of people and guide them. Chacham is knowledge how to preserve the grain.