When you say that the diagonals will still be made on the upper level do you mean they will also be made by standing on the platform or that they will be made by using blocks that are stacked(as I did for the earlier solution)?
Regarding the making of the square block, the only thing I’ve come up with is that one of the blocks needed to push a button has to be in place (presumably stacked on a square block)immediately to the left of the diagonal so that when either the player or a block is pushed onto the diagonal block, the stacked block to the left is sent left and either the player or the block pushed is sent downward. This seems doable aside from it seeming not possible to have that stacked block in place and be on the platform. If you use the risers on the right to elevate yourself then you lose a useful block with that method