Hi!

I've been replaying this game and had a question. I just reached level 12 with my TNO as mage, got the status upgrades, and have been thinking if I shouldn't train back to being a fighter. I'm not particularly enjoying being a mage as I feel the spells are kind of weak and it's really not that fun to do (spellcasting I mean). I wonder if going back to fighter would be ok and if I'd lose anything, power-leveling wise.

You should try to play as a mage. The spells get more powerful and spectacular later on. If you insist on returning back to fighter class, keep in mind that you'll return to the level that you had when you switched to a mage. Also you won't get any HP while leveling up until you reach your mage's class level (precisely you'll receive 1 HP per level until then). You can forget about fighter bonuses for attributes from level 7 and 12 as well. Basically I'd continue playing the game as a mage.