Following up on JonNYC's question, why not book a simple DONEx using CX as the 1st carrier using the online tool? Fly the 1st segment, then redo the itinerary as you want it. Or is there a problem with CX and the online tool?
If one only wants AFRICA-ASIA-USA-EUROPE-AFRICA routing, then all of those restrictions related to travel between Europe and Middle East do not apply. Except the 2 flights ex-UK. Correct?