If you replace them one by one it won't matter at all. This is no slower or more difficult than replacing all at once, and involves less screwing around. The tension is whatever puts the rim back into true.

If you rebuild the wheel with different spokes, you'll need to use two different tensiometer readings, which is a pain.


The wheel doesn't know what kind of spokes it is made of, just how hard the ends are pulling at the rim and hub. You could have a kevlar spoke next to a ti one next to a straight and a bladed.