I could get past the 'blank screen'-problem by exporting it without checking the 'WKWebview on iOS'-option in C2 and checking the 'Use the new Intel XDK project format'-option. Then import the project in intel XDK by opening the project-XDK file.
I edited the 'c2runtime.js'-file and commented out the following lines (result):
After this the simulation works in XDK for iOS devices and the iOS build seems to work on my device. Haven't tested it thoroughly though.