The catch 22 is they can destroy and kill most of Hamas by destroying the tunnels but, put the lives of the hostages at grave risk. What Israel should do is a prisoner swap and halt in fighting only for the exchange of hostages to take place. Then, resume operations because there a no hostages left to worry about. They can do a full bore destruction of the tunnels. The smoke bombs are ingenious and easily reveals the vents of the tunnels. This is where those Tow and Javelin missiles can come handy destroying the tunnels. Or fly drones packed with explosives inside the tunnels.