Yes, as you say the agreement precludes any reduction in LP. The only way would be for both parties to agree to amend (perhaps even completely abrogate, though I think that unlikely) the agreement to deem the previous payments to have paid down the LP.
This time it would be Mnuchin and Calabria conspiring on the amendment instead of Slick Eddie D. and Timmy 'da Weasel' Geithner. While I like our chances much better now, I always consider that anybody who has gotten that far in the political arena is still, well, political, if you know what I mean.