A JQuery Mobile designer is not planned for the near future.
About mixing widgets - using jQuery Mobile widgets inside Kendo UI application is probably possible even now, as jQuery doesn't require a wrapper application to function. We didn't test such integration though, so there may be problems. On the other hand, Kendo UI Mobile widgets are currently not possible to be used without the Kendo UI Mobile Application that initializes them (even if you initialize them one by one). This will probably change in the releases next year, but I cannot give you any specific time frame.
You've missed the Icenium Visual Studio Integration keynote? It has been recorded and posted here.
Looking for tips & tricks directly from the Icenium team? Check out our blog!
Share feedback and vote for features on our Feedback Portal.