>>391667625
Verdant Citadel is one of my favorite single level wads. It is open ended as you can go whatever direction you want to get the skulls needed to visit the last area. It's extremely aesthetic with the level being a large multi layered moss covered castle. It's a Cacoaward winner so you know that it's worthwhile. 

I remember there being a holstering mod. There are multiple weapon wheel mods too. But I have never seen a mod for reloading, partially due to the fact that you don't reload in Doom. Ironically Quake VR added reloading with its last update.