I admit that the thing that is hard to overcome here is Regina executing Marian (I can at least be glad it's clear Regina didn't know it was Marian she was executing though the name wouldn't have stopped her but I bet finding out she's the wife of the man with the lion tattoo even without having have met him at that point she'd NOT have executed and found some ways around it). However I'm not convinced the show is going to let that stand. A&E did say soon after the finale something about it allegedly, and given how we have magic, they simply have to pull out a deus ex machina to explain in truth Regina never did execute Marian. Problem sovled.
This is a show about fairy tales where all of them have collided, it's not hard for me to overlook some stuff. If it were Scandal, Castle, or an actual daytime soap I would have major misgivings but I'm not going to take THIS SHOW that seriously because it's a show that is based on Disney movies which are then based (very loosely in some cases) to the actual fairly tales. I sit back and have fun and not let much of anything bother me at least in regards to punishments for past sins. (Bad writing or acting I will have a problem and I was not happy with Marian showing up but willing to see how it goes).
Finally as to the spoiler of the arrogant prince possibly being Little John, I say bring it on. One of my favorite movies of all time is The Lion in Winter and I hardly think most of the portrayals of historical characters (particularly John) are accurate.