I think the problem with doing that is that the root servers hold a database of top level domain servers. It doesn't change rapidly, but it does change. Unless you could get a feed of the official file from IANA, or a domain transfer (dump of the database) from one of the root servers, you would slowly lose connectivity. If you did get either sort of connectivity, I guess it wouldn't be that hard to to add or subtract what you wanted from the official TLD list.
I think the real complaint is that IANA derives its authority from a $0 contract with the US Department of Commerce, which, under certain conditions, can veto changes in the database. ICANN and IETF are probably also similarly tainted. Would we trust the British, or the wily Canadians, with similar control over our vital infrastructure? I think not.
We have had what are now called ITU-T and ITU-R for decades with everyone being more or less comfortable. I see no particular harm in an ITU-I, with the same bunch of propeller heads doing much the same thing as they are doing now.