Are grail and NEXT, inherently, synergistic? To me, they both grow at a similar rate, and have similar openings and weaknesses. But, seeing grail ICE often makes the runner slow down and rig up, while NEXT relies on rezzing all game in order to be most effective. I'm not convinced that grail does more work here than say, a set of tollbooths and some pop-ups.
If I were looking for a way to marry NEXT and grail, presuming that's the right direction to take the deck, I would probably go harder on having different avenues of program trashing. Aggressive Secretary comes to mind, and Will-o-Wisp wouldn't be bad either if you can afford it.