I think Stansbury had his goals and metrics already--you don't get hired without them. I'm sure there's some tweaking going on, but I think he's gradually implementing his plan.
Criteria should be "if you can make an improvement, make it". A lot of programs will fire a coach, but that doesn't mean that they're better off with the replacement. Fans compare their coach against an ideal coach; no programs ever hire an ideal coach. You have to compare Roof, Sewak, and others against replacements that you think you would get, and you need several better alternatives because plan A often doesn't work out.
If you can't replace Roof with someone significantly better then you're causing disruption for no good reason.