I think you'll find that what you're asking for is already in place. Admittedly not through a single ombudsman, but through this very Meta (or the various SE specific Meta's) as well as through moderators.
They should mediate matters including closed questions, unfair down-votes, and more.
If you hang around for a while on this Meta, you will soon realize that exactly those topics are often addressed here. And we're a rather opinionated bunch, though mostly with good intentions. If we agree with an issue raised, this will be expressed. And the same goes for when we disagree.
Now my use of the word "we" might suggest we act as a collective without individual opinion. Nothing is further from the truth. Debates here can get heated from time to time, with a wide variety of different viewpoints brought forward. A consensus is not always reached, but everybody is able to speak their mind and has a platform to be heard.
Moderators are not afraid to put us in line if we need it, or to take corrective action when necessary on exactly those issues you raise. Nor are we as a community hesitant in calling out (possibly moderation related) issues when we see them.
I'm not sure if all your involvement in the various SE's is visible through your profile, but it seems as if you've only ever asked a single question on Server Fault. Perhaps it's a good idea to participate over there (and perhaps other SE's/SO) for a while and see how things are moderated. If you then still think there is a problem, come back and address it. I think however that you'll find what you're proposing is already in place.
In the end we might not always agree with the outcome of a discussion, or with the decisions taken, but adding a ombudsman would not change that.