I was thinking of getting a Powertap and was curious if anyone knew if I could put the Powertap hub into my Mavic Ksyrium ES wheels or do I need to get the ugly wheel that most Powertaps come in.
Thanks in advance.
It is not possible for that particular set of spokes. That said, why do you want to build up such an unaerodynamic wheel?
You’d be better off selling the Ksyriums and getting the P-tap laced to a nice rim. Since you would be ditching the hub and spokes, all you would retain would be the rim, and a Ksyrium rim is nothing special (kind of heavy). You could get a rim from HED or ZIPP, or any other rim maker, but pulling apart your Ksyriums makes no sense whatsoever.
What wheels wouyld you recommend? Should I go with the Mavic open pro that it comes with?
I am happy with an open pro, but if you don’t like them (for whatever reason), there are loads of options, from box rims to deep rims. it would really depend upon what you’re looking for (and what you’d be willing to pay). You’d probably get more responses here, if you posed a new thread, listed what you were looking for in a PT wheel, and ask for advice…
To be honest I am moving to training with power and the SRM is a bit pricey so Powertap is the next best option but want a good wheel that is stiff and can handle a bigger rider 200lbs…I would like it to be somewhat aesthetically pleasing too. 
If you have the cash, you could do a HED JET with the stallion build. They say that they are good for everyday riding. If you want something cheaper, the open pro is a good rim.