Yaakov personified the כח of קדושה. Thus, Yaakov told Reuvain "Kochi v'reishis oni" - complete שמירת הברית. This could also explain why Yaakov had Yosef swear with his yerech. Rashi says why with respect to Avrohom but not Yaakov. Perhaps it was the chavivos for shemiras habris. Yaakov's excellence in this מדה is also reflected in the fact that מטתו שלימה. Also, Yaakov corresponds to the third brocha of shemona eisrai, the brocha of Kedusha. Yaakov passed on this koach to Yosef. (Could be Reuvain was supposed to get it until he was "chilell yutzai oviv", notice also that Reuvain's other cameo appearance in the Torah is by the דודאים. Which also relate to the מטה of Yaakov; next in line would have been Shimon and Levi - they would seem appropriate after they cried out הכזונה יעשה את אחותנו. But, as explained by Reb Hirsch, their methods were wrong. Shechem and his father deserved death, not an entire innocent city. I heard recently from Rav Aharon Feldman in the name of The Maharal that לא תנאף leads to לא תרצח. It could be the opposite is true as well. Hence they were not ראוי either. Yehuda, too, had the מעשה תמר).
It is Yosef who stood out. By not succumbing to אשת פוטיפר in essence Yosef became an "av" to klal yisroel in inyanai kedusha. Thus, I would suggest, Yaakov told Yosef "amusa hapa'am.... ki odecha chai." Now I can die because this koach hakedusha lives on in you. This can also explain Yaakov's request אל נא תקברני במצרים. Don't let קדושת כלל ישראל get buried in mitzrayim, the country that was the anti-thesis of Kedusha. They were שטופי זמה. Reb Hirsch too sees in Yaakov's request not to be buried in Mitzrayim a deeper message: "pharaoh and the Egyptians would not have taken it kindly had Yakov and his family left and emigrated from Egypt. So, too, the transfer of Yakov's remains to Canaan would not make a good impression, it would clearly show that Yosef's family still did not consider themselves citizens of the land and that they were still emotionally attached to their former country. But the motivation for Yakov's request may be more profound than that. during the 17 years that Yakov lived in mitzrayim he would have seen the powerful influence of האחזו בה on his descendants; he must have seen that they began to regard the Nile as their Jordan, that they had ceased to regard their stay in mitzrayim as an exile. This was indeed sufficient reason for Yakov's entreaty that they should not bury him in mitzrayim." In other word, the mitzrayim saw in Yaakov not being buried in mitzrayim that klal yisroel was not submitting to their corrupt lifestyle. Yosef is the Av who can get us through golus. Even when we are surrounded by a society that is שטופי זמה Yosef has bequeathed us the power to withstand these temptations. And ultimately we will withstand and that is perhaps why chazal say Yaakov Avinu לא מת.
Thank you Hashem for another sober day.