Mediafire sounds pretty good. A 200mb limit is unfortunate, especially for a 25GB BD but it's not impossible.
I was also thinking, how difficult would it be to create a sort of a Blu-Ray skeleton, so that people who have the MKV (which will have the same video stream for the main movie as the BD) could simply download that and then mux it together to create a fully functioning BD? Would that be possible?