It's always either dark, raining, or foggy. Rarely, it seems, do I ever get some clear weather in the dimension. I'd like to be able to adjust how often/long these weather events appear/last.

Some things aren't necessarily weather-related, e.g., blood skies and auroras. It'd be nice to be able to adjust these as well, say, for the dedicated players who want more of a challenge. ;)

Going to C&P this from somewhere else:

The BL config is already getting quite large and imo a bit out of hand, so I'd rather avoid adding more (at least non-compat) config options.

Now that there is a gamerule to disable events changing it should be possible to achieve what you want with command blocks.