What's the best way to edit a script in an ESM? If I can, I'd like to directly edit the ESM, not make a patch. The CS want to save any change to an ESM as a separate ESP.

Download TESGecko and merge the esp with the master file (it's very simple, all you need to do is click a button and choose the esm and esp). But make sure you have permission to upload the altered esm. Since it's unlikely that the esm was made by you I wonder why you don't want to make a 'patch' (almost all Oblivion mods are patches if you see it like that). That's one of the main advantages of using an esm after all, anyone can modify it without any problems as much as he/she likes and the resulting esp is independant from load order.

Okay, cool. Thanks.

I'm not going to upload it. No one would want it. It just removes the need for a mortar and pestle to crush stones from OOO's Geomancy. Makes it compatible with mods that add new alchemy apparatuses (apparati). I don't want to make a patch because I want to keep my ESP number down.