I recommend that you package the main (non derived) system specification requirements in their own containment tree COMPLETELY DECOUPLED FROM (not preempting) specific system blocks; you may then package specific derived requirements near the system blocks they relate to (and they may name those specific system blocks they relate to).
Consider the main system specification requirements a type of contract that (possibly many) specific block designs (with their derived requirements) must meet. For example, one might require that a vehicle system can brake from 100 km/h to 0 km/h within 100m. One solution might involve disc brakes (and a DiscBrake block with derived requirements on the disc material) and another solution might use a drag-car parachute (and a BrakingParachute block with derived requirements on the parachute material).
TIP: you should be able to load your main system specification requirements as a read-only module into a separate design solution project !
