va-eschanan question

i've had a question since last year on a topic related to va-eschanan (I don't think I thought of it, I think a friend of mine brought it up).  i still have no good answer, so I'll just put it out as food for thought, and I'd appreciate any suggestions.

דרש רבי שמלאי מפני מה נתאוה משה רבינו ליכנס לא"י וכי לאכול מפריה הוא צריך או לשבוע מטובה הוא צריך אלא כך אמר משה הרבה מצות נצטוו ישראל ואין מתקיימין אלא בא"י אכנס אני לארץ כדי שיתקיימו כולן על ידי אמר לו הקב"ה כלום אתה מבקש אלא לקבל שכר מעלה אני עליך כאילו עשיתם (sotah 14a)

Basically, the gemara asks, why did moshe want so badly to go into eretz yisrael - did he want the gashmius of tasting its good fruit?  Rather, Moshe rabbeinu said to himself, "there are so many mitzvos that can only be fulfilled in eretz yisrael.  If I go in, I can fulfill all these mitzvos."  Hashem responded back to him, "Why do you want to do mitzvos?  For the reward?  I'll consider it as if you did the mitzvos.

There is a well known machlokes btwn the rambam and the ramban about whether there is a mitzvah of yishuv eretz yisrael - that is, is each and every individual in klal yisrael commanded to live in israel.  (see here where I discuss this more fully).  According to the ramban (who says there is a mitzvah), the whole question of the gemara doesnt get off the ground.  Would we ask, why did moshe want to shake lulav and esrog.  was it to smell the beautiful smell of the esrog? We would never ask such a stupid question, because we know exactly why moshe (or any jew) would want to shake lulav - because its a mitzvah.  why, according to the ramban, is yishuv eretz yisrael different?

Even the answer of the gemara is difficult.  We dont answer, because its a mitzvah to go to israel.  instead, we talk about all the mitzvos that can be fulfilled and all the reward that can be gained from these mitzvos that can only be done in israel.  Again, isnt there a much more fundamental answer - forgetting about what moshe will do after he gets to israel, there is a mitzvah to go to israel.  period.  not for any reason, not to do other mitzvos.  independent of all that, there is a mitzvah to go to israel - why isnt that the answer of the gemara as to moshe's motivation to go into israel?

I might have just thought of an answer.  to be continued...