before you read this is a stupid idea but i think it would "individualize" a Pokemon more.
What would happen if the level a Pokemon learned a move could change? like instead of every single eevee learning quick attack at level 22 some learned it at 21 or 23 possible at 24 or more! then in a VERY SMALL chance (like half the chance of a shiny or less) it may not learn it at all.
Ok start booing me off the stage.......now! Or uhh forever hold your peace