We just did this. On the DDP. We both had the filet for lunch - DD asked for the mashed potatoes and I asked for the maple barbeque sauce and no beurre blanc. No problem with substituting at all.
And the filets were WONDERFUL! Cooked exactly to order and as tasty as we remembered. The maple creme brulee was terrific as well, the s'more was a little less appealing (brownie was a little tough).