This engine doesn't handle large, open areas very well. The compile times on that map are going to be very high (if you can even get it to compile), and the r_speeds (polygon count) will be crazy and make the map basically unplayable for a lot of people. Not to mention with the map being large and open, it will cause a lot of network lag since there is nothing to block players and other items from each other's view, so all the entity data will be sent to everybody playing.
stigma: Using func_wall won't help. It'll convert the world polygons to entity polygons, but they still have to be rendered.
Edit: Can't help but think "TML" stands for "Too much lag".