This is a rare opportunity for Israel to take out a serious threat by removing Hamas from Gaza, while Iran is bogged down in Syria and Iraq. At another time, as you point out, it could be Israel fighting on multiple fronts at once, as Iran lobs long range missiles, short range rockets rain from Lebanon, Gaza and the West Bank; and infiltrators flow by the hundreds or thousands through tunnels; and then a nuke or two goes off.
As long as Hamas rules in Gaza, it will remain a threat to Israel, which will greatly complicate any future war. As painful as it is, it is safer to deal with this threat now, than it is to wait to deal with it while engaged in a multi-front war.
Hamas must be deposed, attrited, outlawed and impoverished.
This missile threat is very serious. The newer missiles incorporate stealth technology and will be harder to stop. It will only be a matter of time before ISIL is armed with these missiles if their rogue state takes hold. Israel faces a grave strategic threat on multiple fronts. It might be wise for them to ally with the Russians who are apparently providing material and leadership training to the Iraqis. ISIL’s offensive has been stalled outside of Baghdad, they are overextended and vulnerable to a counterattack.