The thing that kills me is that Chakotay was never going the extra mile for Seven during her years on the ship. He was ready to drop her during (IIRC) "Dark Frontier", "Infinite Regress" and "Imperfection", when Janeway wasn't. He even admitted in "Hope and Fear that Janeway saw more in her than he could. For him in that last ep to all of a sudden say "WOW, lets do lunch." just seems so out of character.
Then again, for Seven to reciprocate so easily after 4 years of solitude, THAT too seems unlikely.
Speaking of unlikely, how about going from a problem where a strong emotion could shut down her cortical node and kill her without multiple difficult surgical interventions, to a problem that can be healed in one afternoon in sickbay. No need for post op recovery either since she scheduled her date for the same day.
I think the real problem was that between Captain Janeway and Admiral Janeway, there was nothing for C & 7 to "do" in "Endgame"... so TPTB put them into a side story where they (along with Tuvok and 22 other crew members) inspired the Admiral to change history.
The real disservice in this story is that was "all" their characters did.
Quite an igmoninious end to a character (7) that was assailed for taking the lion's share of story lines over the previous 4 years.