I'm not entirely sure how feasible implementing this would be, but do you think that a feature for the "Level Up Moves" editor could be added that gives all Pokemon with updated level up moves in ORAS the same level up moves in XY?
Examples:
- Gyarados learns Hydro Pump at Level 41 in XY, while it learns Hydro Pump at Level 44 in ORAS (due to Crunch [ORAS exclusive] being learned at Level 41).
- Nuzleaf learns Feint Attack at Level 31 in XY, while it learns Feint Attack at Level 24 in ORAS (due to Leaf Blade [ORAS exclusive] being learned at Level 28).
The click of a button could simply replace the Pokemon's XY level up moves with its ORAS level up moves.
Note: I'm aware of Kyogre and Groudon having Origin Pulse and Precipice Blades respectively, although those two Pokemon could simply be excluded from the list.