she'hechiyanu on mitzvos (II)

The Rambam writes (milah 3:3) that the bracha of she’hechiyanu is recited after milah is completed, yet by pidyon haben (bik. 11:5) it is recited before the pidyon (see yesterday’s post). Is a she’hechiyanu like a birchas hamitzvah that must be oiver l’asiyasan, or not? R’ Soloveitchik explained that there is no contradiction in the Rambam. By the pidyon haben, the bracha of she’hechiyanu is on the act of pidyon, and hence is said before giving money to the kohein. By milah, the mitzvah is not merely the act of cutting, but it is the creation of the state of being a “ben bris”. Only after the milah is complete, and the child has entered that covenant, can the bracha of she’hechiyanu be recited.

Perhaps one can bring proof to this idea from the following machlokes: the BH”G paskens that one who was already circumcised and wishes to convert must have a hatafas dam bris, but Rabeinu Chananel (Tosfos Yevamos 46b d”h d’Rav Yosi) disagrees and holds that such a ger does not require anything. Even though the act of milah was done while such an individual was not Jewish, the fact that they are in a state of being mahul is what fulfills the requirement of being a ben bris as a Jew.

Recall from previous discussion that there are two aspects to the mitzvah of tefillin: the mitzvah of doing the act of donning the tefillin, and the mitzvah of being clothed in the tefillin, which according to the Rambam (tefillin 4;25) envelops one in a greater level of kedusha. According to some rishonim, this latter aspect applies only to the shel rosh and not the shel yad. If that be the case, I was wondering when the bracha of she’hechiyanu would be recited– before donning the tefillin, as the ma’aseh mitzvah applies to the shel yad, or only after the complete chalos of being enveloped in tefillin has been reached and the act is complete?