Notes from author
This is a revised version of the main build I use. The main point is to be able to adequately use just about every Dexterity weapon there is (excluding ones that require a good amount of strength, like the Murakumo). In addition, there is a very strong pyromancy presence that can bring a good amount of variation.
I have a variety of Dex weapons I can quickly swap to instead of just the Iaito and I would recommend the same strategy. A Scythe, Great Scythe, Shotel, Falchion, or a Balder Side Sword are fantastic substitutes when the need for them arises. I also often swap out the Dark Silver Tracer for a Black Bow of Pharis or just entirely remove the second weapon for a Flamberge.
You can go with a shield of lesser weight to bring an even greater variety of weapons to bear but that loss of stability will be noticeable.
Good luck with whatever build you choose!