Max Kepler, as a 22 year old, hit 9 homers in 500+ PA's at A+ and AA (almost entirely AA)
Nelson Cruz, as a 22 year old, hit 4 homers 220+ AB's at Short A
Power can develop as players get older--I'm not saying it will for Arraez, and even if it does, it's a gigantic long shot that it would become 30 homer power, but I don't think we should assume Arraez is a slower Ben Revere; after all, Revere, had 15 XBH across 390 AB's (mostly AA, cup of coffee in MLB) at age 22.Arraez has 34 across 503 AB's (SLG of .350 for Revere, .433 for Arraez).
Perhaps a better way to look at it would be this--below are three age 22 seasons;
Player A--.290/.340/.399/.739 in 630 PA's, 34 2B, 4 3B, 7 HR, 7.1% XBH Rate, 40 BB, 74 K, .54 BB/K
Player B--.302/.393/.392/.785 in 476 PA's, 23 2B, 1 3B, 4 HR, 5.9% XBH Rate, 65 BB, 42 K, 1.55 BB/K
Player C--.350/.416/.433/.849 in 566 PA's, 29 2B, 2 3B, 3 HR, 6.0% XBH Rate, 59 BB, 43 K, 1.37 BB/K
Player C is Luis Arraez (with 58% of his PA's in MLB), Player A is Jose Altuve (100% at MLB), Player B is Joe Mauer (100% at Low A).Given that Arraez appears to have plate discipline at least as good as Mauer, if not better, and far better than Altuve, I see no reason to think his ability to put the ball in play will suffer.As he continues to develop power, I suspect he'll settle into a yearly average of 35-40 doubles, and 10-15 homers; more than enough to keep pitchers honest.
In short, I would absolutely offer Arraez a 7 year, $35M contract this offseason, and be willing to go up to 7 and 50 if that's what it takes (although in that scenario I'd tack on a team option for $10M for year 8).