boss battle to gain a lvl every tens

how about having to go through a boss battle to be able to level up?
This could happen every 10 levels (or less at the end)?
I know sometimes it's hard to kill a boss, so you could choose to temporary avoid the boss fight to gain more gils to buy a lot of healing item and projectiles to get ready for the battle, and finally beat the boss.
(in a similar way that after gaining enough XP you can choose between going on battling to earn more gil or posting to gain a level).

To my opinion, the bosses could be more difficult to kill.

Based on Malific's list, here is an apparition order :
-Darksol at the end of lvl 19
-Balbazak 29
-Durahan 39
-Abyss Worm 49
-Bowrider 59
-Ramladu 69
-Cameela 79
-Prism Flower 89
-Laser Eye 94
-Colossus 98

Of course bosses could still appear randomly in the in-between levels, without offering the possibility to level up... wait a minute...
It could be funny to create a kind of shortcut , like you are starting level 32, you encounter by chance the boss of lvl 39 and you beat him , so you jump directly to lvl 33 or even to lvl 40

Please tell me your comments.