Ugh.. looking into it I don't think it can be done without knowing the private key of your dsi. And, speaking from my experience with extracting .wad files (had to do it in order to build an Ikachan WarioWare screenie), obtaining such a key is not for the faint of heart.
I'm not saying that it's impossible, it's just.. unviable. Every person that downloads the mod files would need to dump their dsi's nand, extract the keys, unpack the .bin file using said keys, apply the mod, and repack it using said keys. You can't just apply an .ips file to the .bin file because the private keys used for encryption would be specific to that dsi unit and therefore every person's .bin file would be different.