Sure, it's the newest feature that was added to
GodMode9 v1.4.3, the vram0.img option. You can create a vram0.img file (either FAT or ROMFS) which has the files you want inside of it, then add it to the 'data' folder when compiling GodMode9 from source. The resulting file can be injected to your flashcard and when you boot your flashcard via the magnet method, it'll start GodMode9 and the files you had in vram0.img will be found in M:/vram.mem after mounting it.
As for compatibility, the final size of GodMode9 when compiled with a custom vram is limited by how much space your flashcard can store in it's firm. For the R4i-GOLD 3DS RTS cart which I showed in the video, that limit is 1.4MiB. I hear the AK2i can hold more and the DSTT practically none.