I look at this issue as a marketing tool as well as something I want. With all the brands coming out, all using the excaliber basis, it comes down to what color do you want to look at in your shop. I;m not thinking about starter saws, mid to upper level saws is where I would add it.
All it would take is to retool the table top is to add some tapped holes for clamps to hold the under side tubing, then lock-line for part you position. Dust floats down, if the lock-line is to the side, it will suck in the majority of it, maybe all of it.
The top lock line, like I said, put it inside the upper arm, or on top and remold the upper arm cover to hide it.
One manifold for a vacuum to connect to.
Do not include a vacuum, make it an optional accessory, just as now a light is an option in the upper and mid level saws (starter saws come with them, at least porter cable does).
Cost - yea it would increase cost somewhat, but drastically, I doubt it. And let's face it, most of us buy the machine on a CC which you either pay off, or make payments on, if you make payments, the difference in payment is not going to be much at all. And if it were me selling them, I would just eat the cost increase, and accept a slightly lower margin, sales would flow to my saw I think.