Honestly, I find remaking Valve maps okay if you actually just use the Valve map as a layout or guide to what you want to do.
pl_dbheights is a success because it uses cp_dustbowl and makes it into a nice payload map. It might have started out as a simple remake, but he added more and more as time went by. 1-2 is completely different, with new paths, and the building where the cp was is fully redone. All of 3 has new paths and it's main layout is the same, but there are new places. It's a good remake.
There are some maps that just don't deserve to even exist, like the map that is 2Fort without the bridge and water. He took both bases and nudged them together. [sarcasm]Best map ever, amirite?[/sarcasm]Those I frown upon.
So with this, if you make Sawmill different and keep the theme, it might be a good map. From the screenies, you added a single room that doesn't even go with the theme. So... If you manage to make this great like dbheights, I will commend you.
