randomTickSpeed mostly just effects plants, right? I could make a datapack to set the rTS to 3 when the weather's clear, 6 when raining, and 9 during thunderstorms. Then just have it thunder on load and the starter tree will be 3x speed. No need for crouch spam mod.
Non-foliage effected by randomTick:
These all kinda make sense to speed up in rain.