This game theory sounds reasonable enough. @theinstagibbs will point out that in reality, an attacker can still attempt to cheat without much at stake on ln-penalty by draining their balance in advance. There's basically the same downside for a motivated attacker in either case, but at least under ln-symmetry the node runner who lost state isn't unnecessarily punished, which currently seems to occur far more often.

I'm sympathetic to your argument of "messing with the game theory may increase the likelihood of cheating attempts," but I think the rebuttal is quite reasonable too.