from the info we received the heavy crank was to help with the drive out of corners to make the engine response less nervous, this year they are using a lighter crank with the better electronics, this is all based on the info we received, as i dont work in wsbk i cant say that we are 100% sure of the info we get, but it makes sense to me after working with this engine
i personally belive that there would be a benefit in a lighter crank and we are looking at about 10% i will post reults when we have tested it early next year
I can say with 100% certainty, save your money.
The heavier crank is absolutely critical to stabilize power delivery off the corner and get some rear grip and a little less wheelie. If anything, I'd go heavier. And it has zero to do with reliability.
You can go to a lighter crankshaft with electronics, but not the kind you'll ever get. There's a MotoGP Marelli system ( I have a picture of it somewhere...) that uses an accelerometer to build a 3D model of the bike in real time and perfectly blend power delivery with the beginning of the wheelie. On TV it looks like a mildly floating wheelie that lasts a really long time.
Last I checked, Marelli wanted something like 50K Euro per rider, per year, in licensing fee's and then 250K euro for the equipment and basically you're on your own to tune it.
If you're going to build a crankshaft, do something bad-ass like destroking it 5mm.
EDIT: Also, unless I'm mistaken FIM WSBK rule 188.8.131.52 requires homologated crankshafts with the only weight reduction coming from balancing.