Incinerating 100k people seems to me strategically a waste of a good missile.
You are inviting the death of hundreds of thousands of americans by a reciprocal strike. People in Iran cannot rise up so easily. Dissent is not tolerated. No organized political force exist on the outside to do damage to this regime.
I believe the best way is tactical. Hezbollah today, Hamas tomorrow, Hasaad next and so on. The dominoes are set. Israel will topple the first one. Al others will fiall in their own good time.
I see the logic of your progression. However, I think if assad is engaged, he or iranian proxies at that point will use WMD against Israel and damascus will become a slaughterhouse. The horrible thing to consider is whether iran would back down at that point, seems unlikely.