Feature:

Soot should start as a "non-solid" block and build up over time eventually becoming a full solid block. Chance to build up should be configurable.

Advanced Chimneys is difficult to use without this feature, as soon as the soot builds up the chimneys immediately stop sucking up smoke.

Alternatives:

Another way to do it would be to detect if advanced chimneys is installed and do not create soot if a chimney is within a configurable number of blocks in a configurable radius around a campfire.

Additional info:

I can provide more detail if need be, but this feels relatively straightforward. Until something like this is implemented, I have to disable the soot but I do like the immersion the soot provides... Not an ideal situation to have soot or no soot with no options in between.

Use Sooty Chimneys and modify the loot tables