Actually I have been seriously thinking of it as for one thing the cling wrap we use will not tear but will stretch. By using an elasic band the seal is as good as a rubber seal clamped by a screw lid plus the Hydrometer can be left in the beer and viewed through the top (We do not use glass Carboys). The Co2 being heavier sits on top.
The reason I am interested is that my grommet in the lid of my Fermentor has a lead going to a Fish heater through it and it is not sealed, the Co2 escapes past the lead. I have always used it this way and other than an old blanket I place over the lot for temperature stability, I rely on the blanket of Co2 to prevent contamination. I have a 100% success rate for over 500 brews. maybe our bugs in the Sydney area are less destructive happy bugs.
I do believe in strict steralization of equipment and after seeing some of our wine producers ferment wine, airial contamination does not seem a biggy.
To prevent "Cats, Mice, Possums or Drop Bears from damaging the seal I could always place a board over the top.
The biggest improvement I have made is adopting the use of a secondary clearing container. At this stage I will stick with priming each bottle that has worked every time with perfect success. The beauty of that is that I can stop anytime. Not so if I bulked primed, I would have to complete bottling in one go.
I accept the auguments but I have decided to keep to a system that has proved 100% successful. I will say that I hve had two bottles that exploded in my shed 2 out of 15,000 + bottles. I admit nothings perfect, there is a risk like eating blow fish.