Based on official literatures, it seems like I will not be able to skip immigration and stay within satellite terminal unless Oman Air is willing to interline my bag under separate tickets, officially, they said no (I've asked WY at MCT).

So I have already checked the airport layout, ready to dash off the plane (I'd be among the first to disembark), run toward Aerotrain, turn left and downstairs toward immigration, collect bag, and head back up to BR check-in area on the 5th floor of the terminal. I'm hoping this can be done within 1 hour. At HKG, I can do this under 45 minutes even with moderate queues at immigration.

I do have plan B in case I miss this connection with another backup ticket from CX next day. If things go as planned then I can cancel and get refund for the backup ticket. IMO this is better than getting just one flexible ticket, it will be a few days before CNY so getting another seat next flight will be close to impossible, not to mention having to buy up because of fare bucket.