I doubt any GUI would really be faster than copying an entity file that is somewhat similar to what you would end up with. With Zombie's tool myfist linked you it will show you everything you can put in each line so you don't waste time looking things up.

The Eclipse tool does debug your files, it can catch quite a lot of errors as you make them. I think you might mean IDE, in which case Eclipse is exactly what you are looking for.

Sins entity files are nearly as high level as you can get without the entire process of making information being automated. Seeing as there is such a limited amount you can actually do with the game, a gui really is not necessary. I don't even find the eclipse thing necessary (largely because I don't do abilities), and I iterate a ton of ship information for constant minor changes all over the place.

The manifest update script is super handy. But the process of adding dozens of sound files at a time is much more time consuming than updating the manifest ever was. Which still really isn't time consuming at all.

Also, buying excel. lol

Now, I would have loved if a programmer came along and made something respectable out of that bloody convertxsi.exe code or reverse engineered the particle editor and fixed the insane instability. Alas, I'm used to such silliness by now, what with Stargraft and Arsenal et all.