OK, to get back on topic...
The weight problem in 12th is very little to do with BL against BR, and more to do with the weight of packs and cars going up. In 2006, 3300 cells were surpassed by 3700/3800 cells that weighed 65g each. Even then, most cars weighed in about 820 to 840 grammes.
Today, a 4600 cell weighs 72g, so we've gained 28g on cells alone. Compare that to a BL motor that weighs little more than a BR - about 10g according to my scales, and a speedo that weighs 7g more, again according to my trusty scales. 17g from BL and 28g from 4600s - this isn't a BL problem.
Look at the cars! Since the trusty AE RC12L4, every car I've had weighs about 20g more, and I am guessing that the 12R5 will be even more than that - side shock, adjustment for centre shock, links, front end... My BMI weighs 20g more than my old 12L4! The cars have also contributed to the weight gain.
If weight were that important, then the lightest car would always win. The joy of 12th is that the best driver with the best set-up always wins, whether at Nationals, Worlds or at the Club. BL technology has the least effect on weight increase, and will shortly be back where BR left off.
And if I can get my car down to 830g (and I can) and I will be upgrading to later motors and speedos that weigh less, why should I have to carry 40g of lead to make an arbitrary weight limit? At least the 800g limit keeps costs down and makes tuning easier. Imagine all the "BL and LiPo makes racing easy" brigade who now have to learn to move weight around for the best handling!!
Leave the weight alone, there's more important things in 12th IMHO.