I don't see how it ruins teamplay, except in the cases of using Narc and TAG to guide artillery into a target. As a Clanner you are still going to want your Starmate near you to make sure you don't get overwhelmed by the Inner Sphere surats in their outdated battlemechs, you simply aren't going to be rewarded nearly as well if you focus fire together on one target. If you each select targets and eliminate them (and manage to survive) then you will be rewarded with much honor, which is the behavior the system encourages.
You stated it would ruin team play earlier, then mention below it that the majority of players already play as lone wolfs. This system encourages game play and team work as much as the game already does. Your objective is still to kill the other guys, the only thing this changes is how you do it. If you decide that chasing a single guy through an entire IS company is a good idea, then go for it. Otherwise, let the coward retreat under the superior range of your clan weaponry. If he gets away, then the dishonor is yours to bear. You could fire on other targets around, just make sure not to dishonor yourself more by firing on a starmate's rightful prey or he might get upset.
Seriously though, I see your point, but really, it just comes to down to rewards. The rewards aren't going to stop you from turning your attention away from "the one that got away" to his buddy who isn't fleeing. You just won't get as much of a reward for doing so. However, think of it on the Innersphere side. One of their lancemates retreated, now one of them is taking combined fire and is going to die extremely quickly. In the short term, the clans may have won the battle, but in the long term the clans may not have earned enough honor to upgrade their mechs to something heavier. The IS may have done enough damage to repair, or respawn with a bigger beast, and the pendulum with swing back and forth.
You don't need uneven teams to make it fair. Playing CBT with Battlevalue (MWLL equivalent of C-bills) you could easily make a "balanced" game with even numbers of mechs between IS and Clan. The Clans would simply end up in much lighter machines than the IS team would. That's all I'm proposing here to balance the scaling of clan weaponry into the "insane" range. Remember, this is what makes a Madcat that much more scary than a Warhammer.
The people going for better weapons is fine, the trick is that they are bringing fewer of them to any given battle than the IS. Sure, the clans may have CERPPCs, but they likely can only field one of them on a Uller initially, meanwhile the IS will be fielding two PPCs on their Uziels, or an equally impressive Gauss Rifle on their Hollanders. The CERPPC is better than the IS version, but the IS has the weight advantage to even the playing field.
