First thing u have to know is that,,,, is not a good option, waste tokens to upgrade the stadium. U waste lots of tokens, tokens that u can use during, some seasons, perfectly to win leagues, and champions for sure...

And no, I am not agree, Think that young players can win (as yeasterday my DC) +229 training points in one match, so, young players can be converted easily in 6* or 7* player, if they have 4*... so this is his work. If u wanna have a 6* player go to the scout, and u have it, that's the way.