It looks pretty well elaborated to me.
Basically, implementing what you're asking for takes a big programming configuration that the staff simply does not have the time for.
Ah, I mean "could you go into more detail about the scripts thing?"
Each action and card in the game is run by those LUA files you see in the scripts folder in your YGOPro folder. Those files are also on the server for online play. Once you start an action that is run by those scripts, you have to complete it. Once you start a tribute/normal/special summon of a monster, you can't go back. The script has to be finished.
In order to change this, YGOPro will have to be reprogrammed almost entirely with a different engine to allow you to stop and go back if you change your mind.
I can't explain it any better than that. The bottomline is, the way YGOPro is right now, once you start an action, you have to finish it so choose your moves carefully or go to DN.
I play Yu-Gi-Oh like chess/checkers. Once you take your hand off the card, the action is done. If I make a mistake in YGOPro, oh well. Think it better next time.