An update for those of you who are waiting patiently...
The new costume processor has entered the testing and refinement stage, and its performance is quite satisfactory. It's not ready for prime time yet, but the lion's share of the work has been completed, costumes are being converted, and it won't be long now.
The big problem with the old software is that it abandoned ship if it couldn't find an exact match for every costume element on a character. The reason that's a problem is because the game actually allowed older costumes to exist that use costume elements that aren't available anymore. For the most part, those costume options were updated with enhanced versions, but if one exists and one tiny little thing was off, the old Senticon would just refuse to produce any output.
The new software will always produce a .costume file, even if it can't find an exact match (it will do its best to find the closest match in the event an exact mach isn't available). At worst, this means those one or two legacy elements will prevent the .costume from loading in-game until you click Attempt Costume Fix, at which point you can go in and replace them with something similar.
Some R&D is underway that will enable the processor to automatically migrate costume parts to newer versions where available. This includes things like Armor Plate, Metallic and Tech Sleek (which were updated to incorporate environment reflections in Issue 17), legacy face textures that were upgraded to more detailed versions at some point, and chest detail emblem geometries that got renamed as new jackets and robes came along... just to name a few.