Dirtred, that sounds basically like what I was envisioning from you original statement about the "support structure. It will work just fine. It wouldn't be my preferred method but it will work. For what it's worth, if you have clean joints where the boards mate the glue joint will be stronger than the wood, especially if you're using pine 2x6 boards. It may bow at that length though, so some support structure will be good.
When cabinetman says "slotted" he means you can't just drill a hole that fits your screw size. If you do, the wood "movement" will end up cracking your table. When wood acclimatizes it expands and contracts (the movement) with heat and moisture. If you fix the table top to the support without allowing for the movement of the wood in the top, the top will crack. You can accommodate the movement by making the screw holes "slotted", IE oblong holes that then use some sort of bolt to attach to the top.