117 represents an improvement, but it needs to be fixed.
To name a few points that need adjusting:
The circadian rhythm it's not addressed properly, as it is legal for a pilot to fly very different times, one day from the other. For example you could start flying mid afternoon a day, and very early am the following day, and so on for more than five days. Reserve pilots could be especially exposed to that.
The debrief time should count against the rest time, and it does not. There is a contradiction within 117 itself about this when it's said the rest it's free from any duty, but later it's said the rest start at the end of block time.
The 8 hours opportunity to sleep it's not emphasize properly, and subject to interpretation, therefore 10 hours rest it's not enough in most cases.
12 hours would be more realistically appropriated.
117.21 allows reserve pilots to be on duty for 4 hours longer then line pilots, as the former would be safer to work for longer times. This is particularly concerning, given the fact that reserve pilots are already subjected to more disruption of the circadian rhythm.
The maximum amount of duty, or reserve + duty, should be max 14 hours.
When a pilot exceeds the maximum duty due to deadhead transportation, (compensatory) rest it's either 10 hours or double the deadhead time.
It's should be equivalent to the related flight duty period.
Under 117 if an extension it's required, the company must write an explanation to the FAA of the circumstances and the steps that will be taken to avoid such circumstances to happen in the future. So, if the extension is an exception that must be justified, the pilot should be free to refused it, without having to justify himself with a fatigue call. It is the other way around, it's the exception that must be documented, not the normal operation. This immunity for the pilot from any sort of report should be clearly stated in the regs.