Licensing is applied in CM. You can't apply two different licenses. The only way this may be possible is to have a single license issued by Cloudera that contains the different license versions for each cluster. And I am not sure they can even do that. A quick look at the differences between the two makes me think that it can't be controlled per cluster. My experience as well has been that X feature wasn't available until I had an Enterprise license but once I did it was available in CM.
Now, you could load up another CM and move this cluster to it. That CM and cluster would be running under Express while the others were Enterprised.