1. Would he be a good commissioner for the NHL?
I know most feel he would be terrible, but he is both a partial owner, AND a former player. Like Mario, he would have a lot more objectivity in a lot of matters, and be impartial to both sides.
Both him and Mario remained very silent during the 05 labour dispute (Mario was even still playing), but they might have both been instrumental in getting these labor shortages sorted out sooner. Mario was PLAYING at the same time as being an owner. But he didn't want to ostracize his team-mates, or piss off the other owners.
Many felt like those 2 being more heavily involved would have stopped the labor shortage sooner.
I think Gretzky should be hired by the league in some kind of impartial capacity, but not necessarily in the commissioners role.
2. If the Oilers joined the NHL before 1979, then the Whalers, Nordiques, & Jets would've had the chance to take him in the expansion draft?
Gretzky never should have been exempt from the expansion draft. That was some weird underhanded shady crap that happened.
3. If he had success being the head coach in Arizona, then he would've stayed?
He would have stayed coaching if he was any good at it, but He's a terrible coach for too many reasons.
As with most people who perform at an incredibly high level, he suffers from something called the "Dunning Krugar Effect".
Dunning–Kruger effect - Wikipedia
Gretzky legitimately has an inferiority complex, and honestly believes that everyone is as good (or better) than he is. This is likely one of the key motivations that pushed him to be BETTER than everyone else at hockey. On the flipside, this also makes him completely unrelatable, and a horrible communicator of ideas.
In North American corporate structures, they often promote people to their 'level of incompetence'. This is why Michael Scott's character in 'The Office' was a brilliant salesman, but a horrible regional manager. Gretzky IS the 'Michael Scott' of coaches.
4. If Gretzky chose another sport besides hockey, then who would replace him as the "GOAT"?
Gordie would have remained the GOAT
5. Will there be another player like Gretzky someday, in the NHL?
I don't like saying 'Never', but Gretzky 'broke' they game of hockey, and made it unfair.
Need someone to come in and play the game in a way that kind of exploits something.