Your point "Grinding a longer time each ship give us the chance to find some bugs" is valid. For example - you play tier 1 ship once, maybe twice and you can jump into tier 2 ship, which would mean you didn't even test tier 1 ship fully, meanwhile you need shitloads of matches to grind up in tier 7-8-9-10 and you test them completely...In my opinion every ship should have about the same XP need to unlock it, for example 10-15 matches in EVERY ship, so you could test every ship, not only those who take long time of grinding. (Just in BETA stage). In final release of the game, everything should stay in the same place as it is now.