One of your criteria would actually be okay according to a few CO FA's I have spoken to. And here is a response to the question I raised this week from one:

"Is it also true on a domestic flight that a solo passenger that does not speak English and no crew member speaks her language is able to sit in an exit row? Thanks!"

"Surprisingly yes. Actually, the information we got in training was kind of contradictory. On one hand, they are supposed to be able to understand directions in English, but on the other hand, we were told that we cannot make someone move from the exit row just because they don't speak English. I guess the idea is that as long as they are capable of understanding "OPEN THE EXIT!" in an emergency, it's OK. It's another thing that I personally would change, but that's what they told us. But these things are supposed to be the gate agent's responsibility anyway - FAs aren't supposed to be making that call (although obviously sometimes things slip by and we have to)."