Imagine you are the Head of Compliance at a mid-sized financial institution experiencing rapid growth. Its existing surveillance systems are proving insufficient to effectively combat increasingly sophisticated financial crime risks, including money laundering, terrorist financing, and market manipulation. Your task is to design a comprehensive framework for an enhanced transaction monitoring and market conduct surveillance system. In your design, please outline the key considerations, the essential functionalities the system should possess, and the major challenges you anticipate during its implementation.

假设你是一家中型金融机构的合规负责人。该机构正经历快速增长，现有交易监控系统已显不足，无法有效应对日益复杂的金融犯罪风险（如洗钱、恐怖融资和市场操纵）。请你设计一个全面的交易监控和市场行为监察系统框架。在你的设计中，需要说明你会考虑哪些核心要素、系统应具备哪些关键功能以及在实施过程中可能面临哪些主要挑战。