Choosing Mission Length

I was thinking today what about having a choice of mission length? There's several times I've wanted to start missions at work with only 30 mins before I go home but some missions obviously take longer and by the time I go in the next day the reward is minimal. 

For example:
Minutes = reward
5 = $20
10 = $50
20 = $125
60 = $450
Etc etc. Obviously depending on mission type depends on what reward you get.

Just my thoughts and being able to plan my game better around my time. Thoughts please 

This could work nicely for normal missions. Obviously not for the special missions but if you have set times for jobs it's good to get a quick 15min mission if you can. Every little but help out even if the reward is reduced.

If you know your around a while you can just set a long mission.
+ 1 the idea