A successful managerial past is not always required. Bobby Cox was mediocre in his first go-round with the Braves. 266-323, before the Jays.I didn't agree with resigning Vladdy and Bo at first but the more I think about it the more it makes sense. Of course there is the issue of whether they want to stay here as well.
When was the last time the Jays signed a manager with a successful MLB past? Jim Fregosi? And I wouldn't call his previous record successful except for the 93 Phillies.
Cito Gaston had no experience as a manager.
I get what you're saying, but I don't think that the type of manager you're talking about is very often on the market. Teams keep them until they're past there best before date.