look at it like this.
1. Placing a bypass valve on the cold pipe will create lower initial intake temperatures. When air is compressed it is heated. Why would you want to blow the hot air from your hot pipe into the turbos intake. The reason mazda did it i am sure was to reduce cat light off time as the hotter the intake temps the sooner the fuel will begin to atomize properly in the intake manifold etc. Run some compression formulas out and you will see what I am talking about. If you are going to go through the effort of intercooling it, you might as well reuse your cooler, denser air.
2.
A turbocharger that is surging will have less lag then one that is not. It will however endure more stress on its internals. I would say a bov is more of a protection mod then a performance mod. Think of a WRC car, they wouldnt run any sort of valve, they will just switch the turbo if it actually wore out during the competition. Not to mention the anti-lag ran throughout the course. Those crews can swap a transmission in less then 30 mins easy, think about how long a turbocharger would take and their budget..
3. I was the first guy to do the 50/50 bov/bpv thing. I played with it alot and it really isnt that great compared to swapping the maf to the pressurized side of the intake system. It will work, but in the end I found it not worth the hassle, messy engine bay, two of something for nothing kinda thing. Especially if you are unflashed ecu.