I built this specifically for jflteatt (AT&T) from the cyanogenmod github and a device repo I put together borrowing from all the other GS4s.
Since I don't have the device yet, I can't test it myself, but it should work fine. If it does, I'll get it merged and we'll start nightlies.
Please test & report back.
Today's test build:
http://tau.shadowchild.nl/files/cm-10.1-20130528-Giovanni-jflteatt.zip
there is no need to run loki - the install script does that automatically before boot is flashed. This should be seamless to the user, just flash this the same as any other cyanogenmod install.
This does not require any special recovery process or process on the part of the user. Any booting/properly working custom recovery should work.
REUPLOADED 13:30 EST: Fix the flash - kernel was not flashing. Same link.