You have to make sure 100% to use the correct sized spokes for either side of the rear wheel and front. Reason #1 - Bladed spokes cost alot of money, #2 if you use alloy nipples you can break the resting surface of the nipple off if the spokes dont pass thru the entire nipple.
Things to consider with bladed spokes. To use a spoke thats bladed enough to actualy make a physical aerodynamic differance you would have to slot the hub for the blade to fit thru. CX Ray spokes and DT Swiss's bladed spokes are not a proper blade but more elliptical. SLotting the hub isnt as much a science as its a pain in the ass. It voids all warranty in your hub and creates a serious stress riser. Every track hub ive seen fail was from being slotted.
If you want to build a solid and fast wheel your still better off using a double butted spoke and a brass nipple. Brass nipples have a longer life span. Double butted spokes have the same diameter as an eliptical spoke. Not to mention they're much easier to work with and ALOT cheaper. A well built, super strong and stiff wheel is going to make you faster than a slightly more aerodynamic one.