1. Submerge 6 wooden skewers in a bowl of room temperature water.
2. Preheat grill to medium heat.
3. Place the first 8 ingredients in a large bowl and whisk together until emulsified
4. Peel and de-vein shrimp, Toss in the marinade until completely coated and set aside.
5. Remove skin and core from pineapple, then cut into 1/2 inch wide rings.
6. Sprinkle brown sugar on both sides of each pineapple ring and grill until caramel in color (2-3 minutes per side).
7. Cut pomegranate in half and working over a large bowl, whack the uncut sides with a wooden spoon until all the seeds fall out into the bowl.
8. Roughly chop grilled pineapple and add to the bowl with the pomegranate seeds.
9. Add pineapple juice and cilantro, and mix until well Incorporated.
10. Evenly distribute shrimp on skewers and grill 2 minutes per side.
11. Pour remaining marinade into a small saucepan, place on the hottest part of the grill and bring to a boil. Allow to thicken and reduce by 1/3, then remove from heat.
12. Lay tortillas on grill to heat for about 30 seconds per side. To assemble, evenly distribute Napa cabbage on tortillas. Drizzle each with about a teaspoon of the reduced marinade. Top each with 1 skewers worth of shrimp and a generous tablespoon of pineapple pomegranate salsa.