This is one of those stupid ideas that I've just thought were stupid but I'll put it out there.
Isn't ITV stronger if it is different companies? Because then if one company goes under, the francise can just be re-advertised. With one ITV, if the whole company goes under, then that's it.
I guess that's something you can argue either way, in all sorts of businesses actually. I guess it's countered with the view that due to efficiencies saved in running a larger business there is less chance of it going under in the first place - but as you say if and when it ultimately does the effects are much bigger.