not exist "video passthrough" like audio, it's impossible.
I am not an expert but my Receiver gives me the choice to set an "Output resolution" with upscaling to that resolution or "video passthrough" untouched.
Why can't a media player do something similar?
Obviously subtitles and other overlays need to be parsed first, so it would not be really RAW, see some problems there, but you could be right there are more? Changing aspect ratios is something which i dislike too. Keep you fingers off and reproduce it as it is on the source. Black bars are no problem for me, cutting off parts and deformations are unacceptable. Not everybody's view of course.
Regarding the upscaling job. I have a large collection of DVD's. Tried many media players next to high end Philips and high end Pioneer BD-Players. None of the media players I tried come even close to the DVD picture quality upscaled on my 37/42/55 inch HDTV 's using those BD-players. For native BD 1:1 copies the difference is much smaller but still visible also on smaller TV's. BD-players are my reference regarding picture quality. Keep in mind the topic here is DVD and BD ISO's preferable based on 1:1 copies.
Himedia media players are not part of it yet, but I will find out soon as I ordered a Q10 Pro. I hope it will do a similar job. Will share the results here of course.
Don't say high-end BD-Players are far more expensive than media players, I am aware of that.