If I recall correctly, it takes only 16 algorithms to orient the top 8 edges on a 4x4. The permutation of the edges, however, may take many algorithms because of the permutation possibly requiring and odd number of 2-cycles to solve. This bring me to the idea making the permutation of the edges even while orienting them. There are 2 possibilities between even and odd for both edge cycles making this require 4x16 or 64 algorithms. A large amount of these would be mirrors. 64 is definitely a learnable amount. After the permutation has been made even, the edges would have (4!/2)x(4!/2) or 144 permutations requiring 143 algorithms. This, I think is learnable, but I'm just questioning weather it is efficient to have to recall 1 out of 143 algorithms along side the fact that you cant master all 143. This is the only reasonable system for a 2 look last 8 edges though.
As a side note - I've been wandering why there hasn't been some version of Roux for the 4x4? I've been messing with it some and it seems pretty efficient.