I think a bigger drawback for MLB is the size of the Vegas TV market. It's smaller than Milwaukee.
https://www.stationindex.com/tv/tv-markets
Surprisingly, it's also smaller than Grand Rapids/Kalamazoo/Battle Creek
I think a Vegas baseball team will get plenty of out of town fans like the Raiders do. Probably a good draw for the city in the summer when there might be less tourism.
As for a minor league team + a major league team....I think it makes sense if this was A or A+ ball but AAA seems odd.
That's probably part of the reason he's a 3rd - 5th round projection and not a round 1 projection despite similar stats/measurables to JSN. He may have reached his physical ceiling while a 21 year old still has room for improvement.
To me route running corresponds with your ability to get separation and get open. Davante Adams isn't a huge burner but dude gets open because he is an elite route runner.