What is the worst thing about being a cross-functional team leader?

Though I do not see the worst part as such but since the question has been put forward, would like to answer by mentioning the challenges which are sometimes difficult to handle if not well versed with the different aspects of the domain we are working in .I work in Healthcare IT domain focussing on Proivder(Hospitals) set up.Below are the few of the challenges which a cross functional team leader might face during the course of a Softwared Development Life Cycle :1.Requirement Phase: To freeze the requirements so that the scope is met, the leader should have a domain understanding to an extent .Though the Product Experts and Business Analysts do their part, it is good to have a domain understanding for the leader as well2.Design and Development Phase: The leader should be well versed with the espected scalability of the system to be developed keeping the overall project scope in mind.The timelines planned for delivery should be realistically calculated by considering the resource count and the quality output achievable3.Testing Phase :The application should be tested on different parameters and the leader need to ensure that apart from the functionality being met, the application should pass the Performance testing as well4.Implementation Phase: The Implementation plan should be prepared by taking into consideration all the relevant stakeholders into confidence ,otherwise it creates a delayed "Go Live" schedule.The training should be imparted in a easy to understand manner , ensuring that the Quick reference guides and User Manuals are updated as per the application behaviour5.Change Management: A leader should be in a position to explain the advantages of the application from the end users perspective, then only will the project succeed .Making the end users optimally utilize an application is the key to successful change management .
A leader might face challenges in any of the mentioned phase.
Also sometimes , the leader is involved in Hardware and software requirements , pricing, purchasing issues.Hence , the leader should be well aware of the different requirements which might arise in the project in due course of time.
In a nutshell , a cross functional team leader is expected to be Spealist of All Trades but practically we find "Jack of All trades but master of none" ---and this is the eternal dilemma.
Team members try to figure out the weakness in the leader and once that is known , team leader has no choice but to meet the member demands sometimes unrealistic timelines are made because of inputs from team members who make the most of the ignorance of their team leader in one or other domain areas.