I think it should be a tiered legacy unlock, not strictly legacy 50. For example: Legacy 10 = 2x, 20 = 4x, 30 = 6x, 40 = 8x, and 50 = 12x (just and example). I mean, the whole point of this would be to make the game more alt-friendly. By the time you hit legacy 50, you've probably already levelled a bunch of alts. A tiered system would basically allow the levelling of each alt to be slightly easier than the last, which is the way something like this should work, in my opinion.