Are all the cards the same on the other side, or all the same groupings on the non-address side?
yes, they are all the same on the opposite side, so essentially, the opposite side could be labeled as Master and be inserted after I populate the multiple records, but I cannot figure out how to tell it: "insert master B only on odd or even pages" or something of that effect. So I end up having to manually insert the page in between each back page, and that takes ages.
I presume you don't have a real VDP print module on the printer or you wouldn't be thinking of using Data Merge.
Persoanlly, I'd set it up as two files, print the fronts first from a single-page file as n copies, then print the other side from the merged file. Much faster than re-processing the the same front side over and over again.