Weeeell, it's possible, but it's a VERY roundabout method. It would involve using a PC as well, so it's not a direct R4->3in1->R4. It would be more like PC->R4->3in1->R4->PC->R4.
On the PC, create a Pogoshell compilation with the files you want, up to 32 MB. Put the compiled "flashme.gba" file on your R4's microSD card and flash it to the 3in1's NOR. On the other R4, dump it using GBAldr, then transfer it to a computer and use the "extractFS" program to extract the contents of the Pogoshell compilation. Then do what you want with the individual files, put them on the R4, whatever.
I could go into more detail if you'd like, but I doubt you want to go through all this.