If you have a test manager or a test lead, defining the strategy is that person’s job. You’ll need to review it and make sure you agree with that person’s assessment of the risks.
Decide whether you need a formal system test phase for your product. If you work in a regulated industry and you use an agile life cycle, you can integrate formal system test into every iteration. You’ll need to explain to your auditors how you’re working. In any other life cycle, you’ll need some system-level testing at the end, because that’s where the integration occurs. Only you know how formal you need that last testing part to be.