Well IMHO, the list is almost at that point now, but Tim is right that the powergamers amoung us would leap at the opportunity and blast away, so it would have to be prohibited in some way. Would this work?
[Spitballing on] Healthwarning!! This is very theoretical!
Change co-ordinated fire to be "co-ordinated action" as follows:-TAU Co-ordinated action
The Tau are a highly technical and disciplined race that consequently have the best communications in the empire. They use this to overcome their disadvantage in numbers by closely co-ordinating their movement on the battlefield.
Formations containing Infantry must either be activated with another formation or take a "defensive" action of Marshall, OW or March (we can refine this list later). Other ground formations may be activated in pairs, while air and space fomations must be activated singly.
When a pair of formations activate together to attack the enemy they may either shoot or assault a single enemy formation, but otherwise the pair of formations may take different actions. Any enemy OW fire may be split across the two formations as desired within the rules on range and LoS. Both formations are moved separately to their final locations resolving any OW fire separately on each formation. Once in position, the two formations are then considered a single formation for the purposes of shooting or assaults which then follow the normal rules. The Formations are considered to be separate once the co-ordinated action is ended.
If we wanted to adopt this approach, we would probably have to reduce very slightly the cost and sizes of the basic infantry cadre and infantry support formations along the lines suggested by LiTS. However I would suggest that the upgrades, vehicles and stats would remain the same.