That's a resourceful idea, _,,,^..^,,,_ ! But DrDre is right -- using duplicated frames doesn't help for finding new information for the processed frame.

My thinking was, if there were adjustable parameters in the program, the number of new frames referenced in one direction could be increased to compensate for the lesser number of frames in the other direction:

shot change - (Y) (Z) | A (B) (C) (D) (E)    +0 A +4 == 4 sourced
change +1    - (Y) (Z) | (A) B (C) (D) (E)     +1 B +3 == 4 sourced
change +2    - (Y) (Z) | (A) (B) C (D) (E)     +2 C +2 == 4 sourced

Of course, in a running film, diminishing returns may make this unnoticeable. :D