I think this is a "cross the bridge when we get to it" sort of thing. If this happens and MtF dominate female competition, then there's a conversation to be had about "Well, yeah, we fucked that up, let's go back to the drawing board and see about new rules." If it doesn't happen it can just be like "Welp, no need to worry!"
Then again, I'm aware I'm suggesting this from a position of super privilege - I'm a male athlete and this suggestion couldn't possibly affect me negatively. I wonder if I'd be more biased if I was a female athlete and would be just as open to the "let's see how it turns out" approach.
Then again, I don't really see a better way of seeing if things work out, you know? Most studies I've seen claim there's not a lot(if any) physical advantage to MtF athletes after a certain amount transitioning, so I think it's solid enough grounds for a "Fuck it, let's see how it goes, hopefully everyone is treated fairly and ends up happy" approach.
At the same time, I know it's kind of rich to say that when I don't have to say risk an uneven playing field(though to me that risk seems fairly small). And at the same time I feel like not suggesting anything is also kind of overly privileged of me because of the issues trans athletes have to deal with right now. I kind of keep thinking of the way to address everybody's concerns equally, but honestly I kind of am drawing a blank so I just go back to the not-perfect "Fuck it, give it a shot" approach.
Sports are wonderful, I just want everyone to have a fair shot at them, but I'm not the most informed on how to proceed about doing that. So yeah, my opinion probably comes down to "Fuck it, give it a shot, let's see how it goes, hopefully it's the perfect solution, if not uhhhhhhh we'll cross that bridge when we get to it."