I do not know for certain since I do not own a NEX, but I believe if the donor cart works in the NEX, and the changes to make the repro are not too serious, the repro should work

For example, Earthbound uses an MMC3 mapper and can use Base Wars as a donor cart, so it should work.

Final Fantasy 3 also uses MMC3 and uses a certain Super Mario Bros 2 as a donor. It requires special wiring changes so I am not 100% sure if it would work but I assume it would, since the only wiring changes are to add the extra battery.

Just Breed is MMC5 and would require Castlevania 3 as a donor. No MMC5 games work with the NEX (I think) so I do not believe it would work.


Al