Let's put it this way.
All the fashion data is stored in the fashion block on the save. Injecting a block doesn't merge both blocks, it overwrites the existing block.
The block I have right now doesn't store data on the DLC clothes.
So if you inject it, it overwrites the block existing block in the save.
Now, if you had DLC clothes on your block, and you overwrote it with a block without DLC clothes,
what do you think happens? XD
Well, if you know what you're doing, you can manually hex edit the block to inject clothing.
There's no other editor out there for injecting clothes.
Follow-up (just in case: when will I upload updated blocks?
When I have more time to play through the game and buy the clothes. Maybe in 2 weeks time.
Best not to rush me for it. :3