If you have a mare of equivalent ability or even better than its male rival and the mare automatically is in receipt of 7lbs, then that surely is the issue about having a blanket allowance regardless of ability?
It is why we are getting more top mares going against the males in the top races (even when they have a great race programme for their own sex) and why Champion Hurdles are beiing won by mares more often – there is a strong argument that the likes of Lossiemouth, Honeysuckle and Annie Power would have still won their Champion Hurdles even if they were racing on level weights against the males.
It is one of those things where whatever rule you use there will always be races where it can be taken advantage of if you got a very talented mare.