The Avos and Taryag Mitzvos

I have always had difficulty understanding the concept that the Avos all fulfilled Taryag Motzvos. Part of that difficulty is that virtually NO Yid, even the biggest Tzaddik could do so, as many mitzvos pertain specifically to Kohanim, for example, or to women, or to businesspersons, etc. So realistically, how could they be mekayeim all Taryag Mitzvos?

What I am about to say, might not be a chiddush (I am sure greater minds than I will ever have, have said some version of this thought before), but something occurred to me while sitting in traffic today, and I happened to be thinking of the inyan where Yaakov said, “Im Lavan garti” (and Rashi adds, “V’Taryag mirzvos shamarti,”). Yaakov Avinu was a great Tzaddik, zocheh to not have even one child who was “off the derech” unlike his Avos. But he still could not have been shomer all Taryag mitzvos. What I think that Rashi means, or at least how I understand it, it that “shamarti” comes from the idea of a mishmeres, something that is guarded, that in spite of Yaakov’s exposure to Avoda Zara and Lavan for so many years, he carefully and zealously ensured the continuity of the Jewish people. He was guardian of of the future heritage of his children who would in turn be mekayeim the Taryag Mitzvos collectively in Achdus.

In the same vein, Avraham and Yitzchak were LITERALLY mekayeim (they upheld) the (future) Taryag mitzvos, by ensuring that Klal Yisroel would emananate from them. Their actions of chessed, gevurah, and limud Torah, were the pillars upon which our lives are based.

Anyhow, that’s what I was thinking in the middle of traffic today. I would love to know if there is a mefareish that says this idea. It cannot be new.