[PvK]

As I think Spoon said, however, such a formula can't reduce the choice of to-hit modifiers versus shields to a simple exchange rate, especially given the way SE4 adds to-hit chances.

Since SE4 to-hit mods aren't true factors, but additive modifiers, any such formula would only apply to specific examples requiring all the other factors to be known. Unless you are only fighting one type of enemy unit, and they always fire at the same range, etc, the formula will give different values in each case.

PvK