Thanks for posting this, I love a good and open debate, wether or not we agree on something at the end of it.
There are two reasons that this idea, once implemented, could go wrong, IMHO.
One is that it has be done in other networks (if I remember well, Tsu had something like this) and it didn't work out. So we already have some use cases.
Second reason is a bit more complex. Let's say that we can do something better than the others and our implementation will somehow be better. Even in this case, we cannot go over the fact that reputation is not easy to formalize. Hence, it's very difficult to measure. Yes, there is a reputation number in Steemit profiles, but everybody uses that in order to gauge that person among other users, not as a measure of their actual reputation. People like @ned and @dan have a higher real reputation than their number (and few other witnesses as well, you being one of them, IMHO). Linking this very fuzzy metric to something that can be denominated, that is prone to inflation and deflation, that could be converted in something else will eventually eliminate the very core of the concept.