I'm looking through your code, but it might take me a while to get a good enough understanding of it to experiment with it. I've never worked with CA in polynomial form before. I see the core concept, I'm hoping you're able to work it out. A continuous time solution should be very useful in proving rules as equivalent.

I wanted to make this a separate post in a couple of weeks, but the initial results are relevant. I had a thought that if you use a 4-color 1/2-range CA that alternates between pairs of colors you might be able to find rules equivalent to a 2-color 1-range CA. I just wrote a quick function to check all those possible combinations and got decent results.

Grid[
 Table[
  ArrayPlot[
   Delete[
    CellularAutomaton[
     {
      (((IntegerDigits[firstInd, 2, 4] + 1)*{1, 4^3, 4^12, 
            4^15}) + ((IntegerDigits[secInd, 2, 4]*3)*{4^5, 4^6, 4^9, 
            4^10})) /. List -> Plus, 4, 1/2},
     {{3}, 0},
     50],
    Table[{n}, {n, 2, 50, 2}]](* A list of the alternating rows in each graphic, 
   marked for deletion *)
   ],
  {firstInd, 0, 15}, {secInd, 0, 15}]]

No Rule 30 equivalent though. It's still interesting and I think I'll post some cleaner code at some point later.