You can only plot the possible range of up to 2 cell at once without running into high diminishing returns.
I call that issue the crab conjecture.
If you make each cell rectangular or square and circle round a cell then there are rules for all the cells the circle encompasses.
I have yet to investigate this but it might be possible to alter one sudoku grid with 2 reduced grids and from solving or partially solving an alternative grid you can get reductions relative to the grid your trying to solve.
This all needs to be investigated further although I will move slowly into this field after working on fast factorisation when the internet has changed its encryption so quite a few years yet before I really start working on the issue.