Well, the ability to not have the center inlet is there if you don't have a high heat-load setup or a powerful pump. But it will be there on the prototype because it's definitely a more effective setup.
This block should be so easy to make that experimenting with different nozzles and top configurations would be a piece of cake. The material I've put on the part list for this block comes in 2" so you only need to cut the different pieces to 3" length and then drill/cut the pattern into it.
Here's how you could make it into a white-water clone by simply adding another piece.
This construction method is proving very interesting and will allow for very complicated top without the need for milling. If I can figure out an easy and cheap way of adding nozzles I could make a dirt-cheap storm-esque block too.