First off, to all of you talking about commencing duty while still on a gathering/crafting job: Trust me, you won't get taken into a dungeon by accident while you're still a botanist or leatherworker. /facepalm
I play this game on PS3/PS4 since (re-)launch, and by now the DF "ding" activates some kind of muscle-memory "Am i ready? >> press X / Am i not? >> press O".
After over a year i can't think of more than 2 occasions where i hit commence but wasn't ready, and those were due to almost broken gear, wich, in turn, was 1. due to my own stupidity and 2. is a thing of the past anyways, since i can repair inside a dungeon now.
So, to get into a dungeon by accident, i would have to already be on the right class/job, wich can only be a battle-class. During fights, when holding R2/L2 (to use actions), it kinda negates the ability to hit "commence". For enemy-targeting i mostly use L2+R1 or R2+L1 (feel free to try it, it works really well). And if it really pops the very second i was trying to talk to an NPC... so what? I will stll be right in front of that NPC when i'm done with the dungeon.
But what does happen to me is: I'm queued for duty while i tidy up a room, are in the kitchen or bathroom and hear that all familiar "ding". Now fast, finish this, wash my hands, run back to my room, jump over my couch, hit X on the controller, yay, made it in time to... oh crap! i just hit hold, now to fumble that window back up, go to "commence" and... too late...
It's all about personal preference. And i would personally prefer the cursor to be on "commence" rather than "hold" by default.
But while on the subject of DF, if they do want to improve something, make it so we can hit commence during a NPC-conversation/cutscene or cancel them. As it is now, we can only completely skip the cutscene/conversation or time out the DF. Sure, most cutscenes we can re-watch, but some we can't, and about all normal NPC-conversations (wich often contain valuable info of the story and can be quite long as well) are lost forever if you skip them.