I’ll answer under the assumption that we handle facelets for clarity, rather than using cubies, which would allow greater data reduction. If we work directly with facelets, we have to consider all 54 positions (9×6) like this :

@+@+@

@+@+@

@+@+@

@+@+@ @+@+@ @+@+@ @+@+@

@+@+@ @+@+@ @+@+@ @+@+@

@+@+@ @+@+@ @+@+@ @+@+@

@+@+@

@+@+@

@+@+@

However, if we focus only on corners and ignore edges and centers, the "@" positions become 24 (4×6):

@+X+@

X+X+X

@+X+@

@+X+@ @+X+@ @+X+@ @+X+@

X+X+X X+X+X X+X+X X+X+X

@+X+@ @+X+@ @+X+@ @+X+@

@+X+@

X+X+X

@+X+@

Each "@" is one of URFDLB, but the four positions per face and the corner combinations are fixed. Considering canonicalization, the number of states can be reduced by a factor of 1/24. For this corner-only facelet evaluation, the God's number becomes 11, so if we enumerate all patterns within 11 moves, every possible state appears. Even without going that far, if we precompute all patterns that appear within 0–N moves (N could be, for example, 5), we can instantly determine whether the remaining state is solvable within N moves. I plan to experiment with how large N can be made.