You won’t really need more than a 1:1 gear ratio if you are pushing that amount of power on the climb.
I gather you’ve never done Mt. Washington. I did it two decades ago and used 1:1 gearing and it was a mistake, I should have gone lower. I don’t know what power I put out but based on analytic cycling it was significantly more than the 200 watts the OP expects.
The general rule of thumb is to go well below 1:1 unless you really know what you’re doing.