I think the concentration on Iran's need for nuclear weapons because of its opposition to Israel and the US is a useful smokescreen for all concerned. Yes, Israel sees Iran as a threat, and might lash out because of that, but I don't think Israel sees Iran as an enemy beyond that particular (very important) context.
If I was an Iranian, I would want my country to have nuclear weapons because Pakistan has them (and will have them until at least the time that India gets rid of its nuclear weapons, which is no time soon). Why? Because Pakistan has shown itself vulnerable to religious fervour and pressure, and the nastier aspects of that fervour aren't only directed at the West, but also at Pakistan's Shi'a and Christian minorities.