The British system was very familiar, and while it had potential flaws visible to them at the time they were known familiar flaws. I find it doubtful that someone coming up with an entirely novel and unfamiliar system would have got anywhere at all, no matter how rational and well argued it was. People like familiar and that can affect their judgement. Just worth considering.
I'm not disputing the fact that they took ideas directly from the British government. I disputing the fact that it was done without consideration, reform, or reason. There's ample evidence that they heavily debated each part of the British government that they adopted.
The fact is, the founders remedy for a corrupt president was impeachment. They made that perfectly clear. Corruption included things like misusing the pardon power (High crimes/Bribery).
What they didn't anticipate was the fact that we'd end up with a 2 party system equally spitting the country where neither side would remove their president from office. The put a LOT of faith in "honor" and the fact that the general electorate would punish dishonorable leaders. They did not expect things like wedge issues.
Isn't this true of your own original post?
I don't really understand what argument you're trying to make.
The British approach is more appropriately labeled not as a separation of powers, but a fusion of powers [0] - probably the strongest example of such a government currently around today.
[0] https://en.wikipedia.org/wiki/Fusion_of_powers#United_Kingdo...
The Westminster system subordinates the executive branch to the legislative, but keeps the judicial branch independent.
(In the past, the judicial branch in the UK was not completely separated from the legislative and executive, due to the judicial roles of the House of Lords and the Lord Chancellor, but that all changed in 2005. And other Westminster system countries such as Canada or Australia didn't have that issue.)
State governors have that power.
The role of "governor" isn't defined by any federal laws or rules. It's theoretically possible for a state to decide that it doesn't need a governor.
[1] https://ccresourcecenter.org/state-restoration-profiles/50-s...
The guarantee clause (Article IV section 4) says "The United States shall guarantee to every State in this Union a Republican Form of Government..." What constitutes a "Republican Form of Government"? Is having a governor essential to it?
I think the answer is nobody can really say because the Supreme Court has never had to consider that exact question, and nobody knows how they'd rule if they did. They have previously ruled that the guarantee clause is "non-justiciable" (in Luther v. Borden, 1849), which implies they'd let a state adopt whatever form of government it likes, but they could change their mind about that if they wanted to.
What if a state wanted to adopt the Westminister system, like a Canadian province or Australian state? What would SCOTUS have to say about that?
I am not aware of any corrupt pardons under Obama similar to that of Marc Rich under Clinton, much less more egregiously corrupt pardons like that of Ford by Nixon or Manafort by Trump.
When forming the government the founders didn't just blindly copy British government. There was a lot of debate over what to keep and what to omit (For example, we don't have a king. Presidents were seen as servants not as rulers).
Pardon power is mostly a direct copy of British pardon power. However, there was a reason for that beyond not getting around to reform.
It should also be noted that presidential pardon power, while very powerful, isn't unlimited. The president can only pardon federal crimes, they cannot pardon state crimes. That's an important break from British law where royalty had(?) unlimited power to pardon any crime. Particularly when pardon power was first envisioned, the founders looked towards a very small federal government. In that case, the number of federal crimes were far fewer than what we have today. That means, the presidents pardon power was pretty much only for crimes such as treason.
In other words, absolutely the founders were influenced by British government. They weren't, however, just blindly copying things. Everything went through debate.
[1] https://avalon.law.yale.edu/18th_century/fed74.asp