This is a consistent issue for us, as well. The issue with Labels is we will use multiple so we can set up custom searches, but when you have more than one Label they appear in the order they were added so sorting a test cycle using them doesn't work very well for us.
The best we've been able to cobble together is adding a single Component to each test case, and then each summary starts with an abbreviation for the component and a number to determine the order. For instance one Component might be "User Reports" and the test case Summaries are UR.1, UR.2, UR.3, etc. Then we can at least sort by Component and then eyeball the list to know which test cases to run in which order.
Not at all an elegant solution as adding new or deprecating old test cases results in some creative naming (UR.2a, UR.2b, etc.) but it gives us some ability to sort.
