So I just learned a VERY interesting trick from Nintendo. Apparently, you can force unlink a NNID from a device if you were to reintroduce a NAND that had it linked previously. This means that if you back up the NAND (sys or emu) before doing a system transfer, transfer over all the information to the target 3DS, downgrade then Format the target 3DS, it'll unlink from the target 3DS on their servers. That frees up the target 3DS to add a new NNID. Then what you do is reload your NAND on the source 3DS, go into NNID settings, and when it tells you you can't use this NNID on this system, hold X and Y before pressing OK. This'll ask you if you want to unlink it from the device. Follow through with it then you can relink your old NNID without having to do another system transfer or wait an additional week. This also means that if you screw up the transfer, you can just format the target 3DS to unlink the NNID, reupload your NAND on the source 3DS and still use your NNID on your source 3DS without having to wait. Did anyone else know about this?