In the interest of clarity I think sticking to the current standards makes more sense.

For example it is much clearer to say "I will meet you on Friday at 6:00 p.m. instead of Fridusk" What time would Frinight start?

There are to many different periods in the day that have indistinct start/stop times. I don`t know all of them but you can ask any Jewish person and he will tell you that there is more than just dawn, dusk, morning, noon and night in a day.