Imagine you're a risk manager at an asset management firm, tasked with calculating the Value at Risk (VaR) for a multi-asset portfolio consisting of stocks, bonds, and various derivatives such as options and swaps. Walk me through the primary methods for calculating VaR in this context, detailing the advantages and disadvantages of each. Given this portfolio's composition, which method would you recommend, and what's your rationale? Additionally, what practical challenges or limitations might you face in implementing your chosen method?

一家资产管理公司管理着一个包含股票、债券和一些衍生品（如期权和互换）的多资产组合。作为其风险经理，您被要求计算该组合的VaR。请阐述计算此组合VaR时可采用的几种主要方法，并分析它们各自的优缺点。在此背景下，您会推荐哪种方法？请详细说明您的选择理由，并指出在实际应用中可能面临的挑战和限制。