A lot of good, hard sense in this thread. From where I sit it seems all posters have made a worthwhile contribution. And I detect no significant disagreement as to the way ahead.
I suggest what is needed now is someone with a mathematical bent, with a knowledge of how the game works, to put up a firm summary or proposal. The question at issue seems to be "Modification of attack values of early war (up to mid 1942) engineer troops"