Boolean modifier (bmesh): option to set bevel weight / edge crease for new edges
Mesh modelling isn't really my area anymore so probably someone else should review this and if they consider this a good feature to have.
For the UI layout, 3 long buttons like this isn't really typical. Perhaps use two columns like
|Overlap Threshold||Bevel Weight|
Add an extra underscore: new_edge_bevel_weight for consistency with other RNA properties.
Use Bevel Weight instead of Bevelweight.
Only create the layers and run the loop if the new values are non-zero.