Multi-Processor Systems-on-Chips (MPSoCs) emerge as the predominant platform in embedded real-time applications. A large variety of ubiquitous services should be implemented by embedded systems in a cost- and power-efficient way, yet providing a maximum degree of performance, usability and dependability. By using a scalable Network-on-Chip (NoC) architecture which replaces the traditional point-to-point and bus connections in conjunction with performant IP cores it is possible to use the available performance to consolidate functionality on a single MPSoC platform. But especially when uncritical best-effort applications (e.g., entertainment) and critical applications (e.g., pedestrian detection, electronic stability control) are combined on the same architecture (mixed-criticality), validation faces new challenges. Due to complex resource sharing in MPSoCs the timing behavior becomes more complex and requires new analysis methods. Additionally, applications that may exhibit multiple behaviors corresponding to different operating modes (e.g., initialization mode, fault-recovery mode) need to be also considered in the design of mixed-critical MPSoCs. In this paper, challenges in the design of mixed-critical systems are discussed and formal analysis solutions which consider shared resources, NoC communication, multi-mode applications and their reliabilities are proposed.