I have never even vaguely contemplated using overcharge on anything, and after my first experience with the BFG 10k, which resulted in my death deep in an AAo666 run, I just pick it up and drop it to register the find. I can also say that even with MAc, the ammo cost is obscene - but I suppose that part, at least, makes sense for a rapidfire BFG.(It's also worth noting that the combination of MAc and N1, the only way to make this a weapon that could be used even occasionally[and still not as a primary weapon - maybe more along the lines of a plasma rifle to a player without MAc in a standard game], are impossible since they come from different classes). I can maybe see it being useful for the JC fight, but even then, there are much more efficient ways to use energy cells, and good luck finding it outside of Ao100/AAo666, anyway, where JC doesn't spawn, his open arena doesn't spawn, and his closest analog prohibits the use of the BFG 10k anyway.
So I agree that some changes need to be made.