The OpenType [1] font format does allow for stylistic alternates [2], which is basically what you're suggesting, in that different forms of characters are included and can be selected based on rules (like ligatures) or I believe selected at random. When used with a handwriting font it does more closely resemble natural handwriting to the casual observer.

[1] https://en.wikipedia.org/wiki/OpenType#Advanced_typography [2] https://en.wikipedia.org/wiki/Font#Character_variants