Martinez would have been great, but again, whether him staying would have helped alleviate the malaise that has set in around the club I don't know. Villa are a team that are looking to move up and have bought players to believe in that vision and Martinez feeds off of that and vice versa.
Decision to keep Leno was not a bad one given how well he played, but you have to make sure he is happy and keep the conditions right otherwise what's the point. In the same way, who knows whether Martinez would have been annoyed at some of decision making and likewise become unsettled.