So the valid points you guys bring to the table is the fact that it really isnt training if you end up fighting a core opponent.
However, recently ive only really seen arm training games and only one core training game, this really isnt fair to those who play core accounts. This encourages newer users to make arm accounts which will only worsen the problem.
How about instead of naming it Training_all, we satisfy the story by naming it skirmish.
Optional, and more difficult to code obviously: If you really want to satisfy it there should be 2 teachers in skirmish mode, and skirmish games are limited to 2 on 2 or greater (2 arm+, 2 core+) One arm teacher, the rest would be students, and one core teacher, rest are students. If in the case that there is only one core or one arm, the core or arm player do not gain any points teacher or student.
The basic idea here is that the fight takes place in a random planet in the universe where an experienced commander takes a lesser experinced one to the battlefield for some 'real' training.