As an extension to mod support. The basic level editor is now up and running. Just in the process of adding the tile/object pallet and the edit tools.
The primary motivation for the Editor this early, is so I can create test maps for validating skill / level object behaviour.
Both the Editor and Player use the same code base which means the Editor allows you to rapidly flip between Edit and Play mode without having to save or launch L2Player. This means that editing and testing has a tight iteration loop.
I have also implemented a transparent file system wrapper so that mods can replace all aspects of what is in the base cache without actually touching the base game data. All graphics are in .png format for easy manipulation. Graphics which are part of a sprite sheet and have an accompanying .spt file will get a dedicated tool in the future for unpacking/packing sprites and specifying animation frames.
This means for e.g. You place a copy of menu_0.png from data/cache/ui/screens in data/mods/yourmodname/ui/screens, it will be used in place of the original title screen.
Quick early preview of Editor:
https://youtu.be/9vRA5pQoZu8 (Again using the Tribes of Steel level pack - Thanks Ste Woz Ere

)