I was trying to get the same level up tweak to work for my Athambia Academy submission (as students gaining experience through duels). One issue I ran into was how to ensure backwards compatibility with RoE. This card works fine with Time of Heroes and Champion's Drake, but not Venerated Teacher (when venerated teacher enters the battlefield, put two level counters on each creature you control with level up). Any idea on how to make that interaction work?
Is it possible to give it Level Up - Attack?
The issue with Level Up - Attack is Level Up can only be activated as a sorcery, so you would never be able to Level the Creature up. The issue you are facing is that you are trying to be creative with a bad keyword design. I think you have to leave the card as is and sacrifice some of the level up interaction.