Handicap from a Torah Lens

There are few topics in the Torah that baffle me as much as how the Torah views handicap. Every year I re-read the Torah's prohibition on service on the part of priests, or Kohanim in the Beit Hamikdash. The prohibition is a blanket one, and uncategorical; no one who has one of the listed physical ailments, all of which are visible to the naked eye, can serve God on behalf of the Jewish people. They are not allowed to enter certain areas, they cannot pour libations, or sprinkle blood on the altar. They cannot serve to effectuate the repentance, needed or sought, by the masses of the Jewish people.

In a beit knesset I frequent on a weekly basis there is such a Kohen. I don't know the medical background or name for such a condition, but he has one leg that is far shorter than the next. He wears an elevated – platform – shoe, which enables him to walk, but when he walks he limps horribly, contorting his whole body with each step. Every day he does birkat ha'kohanim, i.e. the performance of the priestly blessing. I don't know if his handicap would invalidate him from service in the Beit Hamikdash, but I do know, that when it comes to the daily priestly blessing some concessions are applied, most prominently, if the congregation is used to the handicap of the particular person, in some instances, it may not invalidate the Kohen from blessing the community. The same stipulation applies for other factors that could potentially preclude the performance of the priestly blessing; were a Kohen's clothing to be besmirched with clay, typically invalidating, but that notwithstanding, the garbs of the other congregants similarly muddied because of the work they do, then the congregant who is a priest would not stand out and be odious to the congregation.   

I have heard many opinions, mostly modern, as to why a handicap would be invalidating. It would seem to be that once upon a time it was implicitly understood why a handicap could serve to invalidate a person; the Torah clearly states, and reiterates that though he is fully from the "offspring of Aharon," the blemish he has rules out any temple service. The very same verse states that he will be perennially holy and that nothing can detract from his holiness; he can eat Terumah which would warrant premature death by divine decree for a non-Kohen.

At the end of the day, we cannot help but wonder whether any interpretation we gave the matter wouldn't be anachronistic, i.e. applying modern norms to biblical ones that are far different from our current conception. A friend, Motti Rosenzweig, suggested that perhaps the reason for the prohibition on priestly service has to do with the fact that someone who is handicapped needs assistance from others. Someone serving in an official capacity needs full autonomy when it's on a representative, or judicial level. He can't be beholden to anyone, and similarly, one who sits on a Sanhedrin, or Jewish court of law, need also be complete in bodily form, i.e. without handicap. It would seem that what my dear friend shared seems to dovetail with the very simple meaning, or p'shat, that there can't be any construal  that the representative agent wasn't acting in full capacity, but rather acted, even in most minute part, as the proxy of someone else, whatever the handicap may be.