I would prefer a max player who has already proven he's a max player.
When you give out max contracts to players you hope will be a max player, that can get you in trouble.
Not saying you shouldn't do it, but you have to be careful, and I'm guessing Barnes would be pretty far down the list when it comes to the moves Danny is trying to make.
There are 1-2 of those players this year (Durant and maybe Horford). Furthermore, there are multiple types of max contract values -- those for players with 0-6 year of experience (Barnes' category), those with 7-9 (Durant and Horford), and those with 10+ (LeBron). Max players in the first group will get about $21 million next year, in the middle group will get about $26 million, and in the last group will get over $30 million. Furthermore, with another cap jump coming in the summer of 2017, those numbers should increase another 20%.
When people think of a max player that we can get, obviously they think Durant. But KD is likely to sign a 1-year deal this year and then a 4-year deal next summer. This year he would get about $26 million, and next summer, since he would now be in the 10+ years of experience category, would get around $36 million. Meanwhile Barnes would sign a 4-year deal this summer (presumably), which would pay him about $21 million this summer, and $22 million next summer. This summer he might seem to be overpaid, but next summer, when players like Durant and Chris Paul will get $36 million, and Blake Griffin and Stephen Curry $31 million, $22 million doesn't seem nearly as unreasonable. Next summer it wouldn't surprise me if Nerlens Noel gets the max of $25 million for his experience category.
It's looking to be a very weird free agency market the next couple of summers. Normally the max salaries increase 5% between years, not 20-30%. And at the same time, normally there aren't 20+ teams with max room. Including our cap holds for first round picks, (but excluding non-guaranteed deals and free agents) the Celtics have currently have 12 players under contract next season at $40 million dollars. This gives them $50 or so million to spend on 3 contracts using only cap room. There's a certain point when sitting on your pile of cash doesn't make sense, and this might be one of those summers.