Some might say there are several reasons one might wish to impeach Cheney.
However, in my opinion, one overrides them all:
What? You don’t want to follow my link?
OK. As everyone knows, the Senate presides over an impeachment trial.
And the Vice President presides over the Senate.
There is one exception, when the President is tried, because it has been foreseen that there would be a conflict of interest.
But since the language was written back in the days when the Vice President did nothing. No one foresaw there would ever be a desire to impeach the Vice President. So no exception is written for this case. Cheney would preside over his own impeachment trial.
And there’s only one way this situation will be fixed.