I don't think it's the same problem if you have twice the memory in one case, vs six-to-eight times the memory, in the other.
Wii U haven't 6-8 times ps360 memory (maybe you are refering to ps4-x720) ... so if you have a downport to wii u you can "downport" again from this version. You only have to cut more XD.
Besides a "twice" amount can be 2+ gb of difference, not a "small" difference in my opinion to make downports an easy thing.