Spears want a word ...
Spears fighting in two ranks is something that you have to pay for.
Also spears are quite a weak weapon, the range is what gives them their advantage. There is a massive difference gameplay wise between something that is S3 (or maybe S4) fighting in 2 ranks and something that is S5 or S6 (great weapons, ceremonial halberds etc) fighting in two ranks.
Like an Empire parent unit with 2 detachments fighting in 2 ranks would have somewhere in the region of 33 attacks (assuming none of them died). That is a truly stupid number of St4 attacks to be pumping out for 215 points.
An increase in CR (through returning the +1 CR for outnumber or the third rank for example) or a decrease in monster output (through removing stomps and the triple save) would be much much better solves.
Broke WHFB? That's a bit overly dramatic, isn't it? 6th is the edition of WHFB I enjoyed the most, and I think many feel that way. So, why do you think that the +1 AS bonus in melee broke the game?
I think he means that the fighting in 2 ranks broke WHFB in 8th edition. If GW bring in fighting in 2 ranks for infantry it will show they haven't learnt anything from the 8th edition disaster.
Maybe the front fighting rank can attack no matter the casualties via step up rule, provided there is enough bodies to refill the fighting rank. This benefit would not affect the flanks and rear casualties inflicted.
This might help but I don't think it would given the possibility of wide fighting ranks.
I suppose there is a question about what you want to solve. ATM infantry is generally fine against other infantry. It is weak against cavalry an large monsters. Maybe infantry should get a strength in number rule or something.
Infantry will give ground instead of fall back in good order against any non infantry troop type against which it has a higher unit strength and is fighting in the front. This would power up infantry against monsters and cavalry without increasing the damage output at all. It also means that you can slam a large unit of calvary into a small unit of infantry with no concern but a small unit of calvary will have difficulty with a large unit of infantry.
However it only applies to the front.
Of course the difficulty is that this is what shieldwall does. Though maybe shieldwall would retain its advantage because you can use it to the flank and rear.