Love this! Just an idea/suggestion, but you could define some variables like chance to spread, maximum and minimum growth speed, etc, and then randomize both the physical spread and timing :)

Good catch! The new version now has random growth time customizable from the mod settings.

Here's an idea, use a global fractal noise map that defines the growth speed for each tile so that there are local regions where the tiles grow faster

Not worth the effort. There's already a randomization system in place.

Sure, but it's cool! :)