Vegas has nothing to do with the Flyers, if Hextall wanted to emulate Vegas he'd do what Shero has done in Jersey, trade 3 2nd rd picks and throw in a couple 3rd and 4th rd picks and sign a couple free agents and add a bunch of guys in their mid- to late 20s who are competent third line winger types and fill out the lines. It's a quick and dirty rebuild, but it only works for a couple years, then some of those players become the current version of Read.
The other model is Toronto, really suck for five years, accumulate a bunch of top 10 picks, then bring in a successful coach, sign a few older free agents to mentor your young stars and away we go.
A case could be made that Hextall should have blown it up, tanked for a few years, but despite being competitive he has landed Provorov and Patrick and has a bunch of prospects with a chance to develop into top players. So he's not far behind where he'd have been if he deliberately tanked (probably couldn't have gotten much more in trades), and I'm not sure the TPTB would have signed off on a total tank.