So, in essence churchill only knew of what has existed and what has been tried, not what is to come or what is possible.
I'll take a constitutional republic, minus special interests.
Yes, I would think that is an accurate interpretation of what he said. Well, it appears that we have about half of what you desire--although in a complex technologically and economically advanced civilaztion like ours, it would be difficult to cut out the special interests. They often provide an extra-governmental system of checks and balances. They also breed corruption.
That being said, it is part of the price we pay for our system. We pay a price for our freedoms (and forgive me if I sound like I'm lecturing to you because you are obviously bright and well read and I don't mean to), such as having my kids listen to stuff I don't want them to (First Amendment) and the ability of criminals to easily obtain handguns (Second Amendment). It becomes the lesser of prices to be paid if we did not have the Bill of Rights.