On your #1, I get that, but it seems to me that an Impeachment vote is something totally different from every other House voting issue. It is, or should be, an extraordinary measure, and I wonder if that would justify an extraordinary threshold.
#2 is a fair point.
I absolutely agree with #3, and that's really kind of why I'm intrigued by Scott's suggestion - why have the circus, and all its costs (financial, time, emotional, political) if you don't have a realistic chance of pushing it through?
Also, just a thought on your last point regarding the media: That should be true, but we've seen media really choose sides in the last 2 decades. At this point, the media biased towards the accused side is going to claim "bogus charges" unless it's something that both sides want to get behind.