There are several parts to assaults that can be perceived as unfair.
- The direction of counter-charges, which can 'pin' defending units
- The way that supports do not suffer damage.
- The way that the assault is limited, which tends to favour the attacker (naturally).
Spit-balling a little, I did wonder whether it was worth allowing the defender to increase the area of assault, and also perhaps allowing each participant to choose to allocate some hits to enemy supports (the assault resolution is still determined by the original attacking and defending formations).
The modifications might look like this:-
1) the attacker activates and charges under the current rules
2) the defender countercharges under the current rules
3) the defender may choose to increase the area of the assault by adding some or all units that are outside the the assault range of the attacker but within 15 cm of any other enemy unit. This makes these units eligible targets for enemy support fire under the usual rules
4) The attacker and defender may elect to split their fire, allocating up to half of their dice to enemy supports as follows:-
a) First the defending formation sets aside up to half of it's dice for shooting at enemy supports, then the attacker sets aside up to half of its dice
5) Attacker and defender exchange fire under the current rules, but potentially with fewer dice
6) If the assault continues, the attacker and defender exchange fire with the supports. Any hits on Supporting formations are handled under the normal shooting rules. Note to allocate dice to any target, one or more assaulting units need to be in range (15cm) and LoS as usual.
7) Assault resolution is performed as usual, considering the factors and hits relevant to the attacking and defending formations as usual.
The point of this is to allow the defender a little more control over the assault (or requires the attacker to be a little more cautious). More importantly, it may make the assault mechanism more acceptable. In practice, I have a suspicion that the defender may not take advantage of these options in the end, though being able to damage supports as you are overrun may have its appeal

.