I've been thinking about this problem of 'fire, retreat behind hill, reload, move forward, fire, retreat etc'. There ought to be some incentive for an infantryman to stand still, and I was thinking perhaps one of these could be in the form a the following implementation: for those who stand still the firing reticle gets smaller, slowly but surely and to advantageous effect. By staying still and being a little patient (carrying the risk of being shot) you get an accuracy bonus. This would hopefully balance the 'fire, retreat, reload' tactic a bit more, so that it could be re-introduced.
I'm pretty sure this would give some incentive to staying still in line, as well as actually make shooting more skill-based in general; careful, patient judgement of a player could result in a more accurate shot, in the same way that a moving player sacrifices accuracy of shot for maneuverability. The more that player judgement affects the result the more skill-oriented the game will be.
Another idea is to make one situation contra to reality, for the sake of balance: make firing whilst standing slightly, but noticeably more accurate than whilst crouching. This would once again encourage standing lines more and perhaps enable crouch to be reintroduced into LBs, it now having a downside.
What do you think? Rules aren't the only solution you know. This mod isn't near finished yet and modding changed are definitely a potential way of balancing aspects of LBs or giving them more variety.