I've been thinking about this, and while I know the Clans usually would not even consider C3, I do see it as fitting for use in protomechs. The Clan aversion to this technology is due almost entirely to thier ideal of one-on-one battles, while C3 is useful for enhancing cooperation in battle. However, in real warfare that ideal comes down to one point-on-one point. So Clan warriors of some types do cooperate. Battle armor for example, although on them C3 would be useless since the whole point stays together and thus unable to make use of it's advantages.
But Protomechs are different. The Point fights together as one unit, but do not stay together in one hex. Thus, C3 would be a boon to them as they could coordinate themselves better to fight an opponent. So, this brings me to two questions. 1) is my logic sound and 2) how much should a C3 device able to link up the 5 protos of a point weigh?