Use by proxies would still result in retaliation against Iran. Which is why nuclear powers insist on absolute control over those materials. And also why there is no historical precedent for a state having transferred nuclear weapons to a non-state actor. All of which is to say that, while the issue of proxies isn't irrelevant, it shouldn't be driving policy decisions. A likely more effective way would be to formalize Iran's participation in the Nuclear Club and in the creation of transparent command-and-control functions in order to affirm Iran's deterrence-motivated intentions. Of course, that would require modification of the respective narratives prevailing in Jerusalem and Washington.
US rally shows support for ex-Marine held by Iran on spying charges (AP)
from the article: Insanity, not logic, guides Israel's leadership