A/ next time make it an actual poll so people are forced to make an actual decision and you get hard data to drive your choice / learning experience
B/ poor planning leads to hard choices. Cough it up and learn to build buffer, treating orange as red, because flexibility is what buffer is for
C/ or put in your goal rules the clear-cut ‘if someone I didn’t see in 3mo+ asks for my time, I get to weasel out’ (or make an explicit list of the people who can trigger this, effectively saying “I stick to my schedule except for those people”)
B+/ on the beeminder side, it would be a nice extra functionality to ‘bank and hide’ a bit of buffer instead of retroratchetting, effectively setting yourself an artificial deadline, with the proper deadline colors (something like this).