Hm, garnering wages in this way (ie as if paying off a debt which matches the cost of their crime) might disproportionally affect the poor. For example, assuming no overhead, a person who makes 50k year could pay off a 100k in 2 years, whereas a person who makes 10k a year would pay it off in 10. This may actually have an effect opposite of what OP seemed to be intending — the punishment should have equal weight to everyone.
Perhaps a way to improve your idea to mitigate the mentioned issue would be to also scale the total fine to be repayed by income. Sort of like a progressive income tax.