Hexagonal hatched polygons Altium
I managed to achieve a hexagonal hatch by using a solid polygon pour, and a series of hexagonal polygon pour cutouts. Its not the quickest or most accurate, but without knowledge of scripting or some complicated import process, its the simplest way to do it. 

Start by drawing a hexagon with lines, (you may need to do some trigonometry to be accurate) then use the polygon pour cutout to go over it, and then a lot of copy and pasting.