BDD with Manual Tests?

We are switching from a classic 'Waterfall' model into more Agile-orient philosophy. We decided to give BDD a try (Cucumber), but we have some issues with migrating some of our 'old' mythologies. The biggest question mark is how manual tests integrates into the cycle.

Let's say the Project Manager defined the Feature and some basic Scenario Outlines. With the test team, we defined around 40 Scenarios for this feature. Some are not possible to automatically test, which means they will have to be tested manually. Execute manual testing when all you have is the feature file, feels wrong. We want to be able to see past failure rate of tests for example. Most of the Test-Cases managers support such features, but they can't work with Feature files. Maintaining the Manual Testcases in external Test-Case manager, will cause never-ending updating issues between the Feature file and the Test-Case manager.

I'm interested to hear if anyone is able to cover this 'mid-ground' and how.