the biggest con is the fact you think its cheap insurance.............
things such as the ignition system, electrical system, clutch fan, transmission will all still be affected by deep water crossings. water deep enough to get into your tranny, or contact the fan will send mud shooting everywhere; into electronics, etc.
in short, yes it will stop your engine from hydrolocking, but won't make your jeep waterproof!!!!!!!!!
best bet is to check the hole before you drive through it.............. grab a stick (usually lots around) and feel for the bottom of a hole....... if you lose the stick, chances are you'll lose the jeep......