> add a mechanism to create many more universes when a correct result is hit
Simple count has not much to do with the outcome observed, IMU each branch in a split is not equally likely. If you finely sub-divide a low-probability branch into 2^300 sub-branches, so what. Instead, you need to merge multiple high probability branches back into a single outcome that is observed "99.99999% of the time".
In many worlds the probability observed can absolutely be thought of as the ratio of worlds with that outcome vs another. Any specific numbers here are just as an example.
Simple count has not much to do with the outcome observed, IMU each branch in a split is not equally likely. If you finely sub-divide a low-probability branch into 2^300 sub-branches, so what. Instead, you need to merge multiple high probability branches back into a single outcome that is observed "99.99999% of the time".