Yes. In fact, if you are in a user organisation, it would be strange not to customise it – because MoReq2 contains many generic requirements, such as “the ERMS must do either this or that”, and “the ERMS must respond within <xx> seconds”. In these cases, you need to choose between "this" and "that"; and you need to decide how many seconds are appropriate for your circumstances. You are also likely to need to add requirements for your operating system environment, for interfaces to other systems, etc.

Appendix 3 of MoReq2 contains advice on how to customise the requirements.