There are several mods that expand your game with cool pieces, without taking from anything.
It would be cool if you could incorporate those pieces - and expand them into the DLCs where modders have no access.
For example basic building styles can be enhanced with pythagoras pieces, walls (and windows) that have twice an inside or an outside visual, smaller gates, rounded windows (with metal bars for the hole), doors that are in the middle of two walls, etc.
Thats really nice. Whats sad is, that these parts are only avaiable for basic building styles, OR mod included styles. While the nice looking DLCs you sell miss out on those parts, and therefore get less awesome.
A cool solution would be to incorporate those building pieces in your base game and expand to your DLCs.
OR you could make it possible for modders to make parts that rely on DLCs, so such pieces could be made avaiable for the additional building styles you add without you doing work.