Huh, sounds interesting, but why not just throw real fast consecutive jab cross combinations?

Because it's a cross comination and not a strieght line. The princeable behind it is speed/quickness vs power.

the straight blast gets it's power from foot work and the momentum of the chain of punches where cross combination of jabs would get it from turning your waiste. The jab, or a hook bot have a much more angular feel to them. The other thing, is jabs work good in a few stances, but straight blast works in almost any stance. Try a few, like try to do streight blast and a jab in horse stance, Your balance will be off and the jab will lose a ton of power.

The other thing is that the streight blast executes the one inch punch technique of closing the fist before impact and punch 2 inches behind the target, which doesn't work so well with the jab btw. Therefore if its twice as fast as the jab, it has a chance of being just as powerfull as the jab as well.

I would train in it, and get to know it, and then spar using that and then using the jab combo. Find what you prefer, and what works better, and use that.