Hi,
I would suggest you to maintain a single material code and maintain the conversion factors in different alternate UOM.
For example, you may define different UOM for small carton (say "SCA", 1 SCA = 6 pieces in material master), and big carton (say BCA, 1 BCA = 12 pieces in material master), in CUNI transaction. The corresponding EAN number can be maintained in additional data in material master.
Similarly, maintain different UOM for pallets, one for small pallet (1 pallet = 420 pieces) and one for big pallet (1 pallet = 480 pieces)
Once the UOM is maintained correctly, use the variable order unit in purchasing view as 1. This will allow you to order in different order units. If you want different price based on different order unit, maintain the variable order unit as 2 in material master.
Please check the feasibility of the option and revert back with your concerns / query.
Regards,
AKPT