Bellows can speed up the firing of pottery, etc, in a pit kiln when actively worked.
This would be the equivalent of raising the forges/crucibles temperature to heat things more.

Since we don't have a modern kiln, this seems like a fair trade off.

First off, you can already use the forge + bellows as a pit kiln.
Second off, if you have something not a bug, then don't use the "bug report" template.
Third, suggestions for new mechanics are better suited for discord discussion rather than issues on github.