Are these things full recourse? Because while a doubling sounds quite nice, you would need to earn 25% from the current state of 800M to break even on that additional collateral of 200M. Sounds strictly worse than just liquidating the original loan to achieve net zero and then doing a different loan with your 200M of extra assets.
If you can liquidate 800M to rid yourself of a 1B loan then it seems fairly obvious to do it?