I would personally go for an either physical/ special Lucario, not mixed, but that's just me.
The user copies the move that the target has selected in that turn and uses that move itself, with the power boosted by 1.5x. Me First will fail if the target moves before the user, or if the target uses a non-damaging attack. If Me First is used on the recharge turn of a move that requires the user to forfeit a turn after its use, then Me First will copy said attack regardless. This move cannot be blocked by Substitute for the purposes of copying the move used on that turn. The following damaging moves cannot be copied by Me First:
>Chatter
Counter
Covet
Focus Punch
Me First
Metal Burst
Mirror Coat
Struggle
Thief
I find Me First to be a really gimmicky move. You don't know what your opponent is going to do next, and if they use a priority move you'll have wasted a turn. If they use a non-damaging move you'll have wasted a turn. If they're faster than you (scarfed Pokemon, Deoxy's speed), you'll have wasted a turn. Even if it does succeed, the move Me First copies might not be very effective on your opponent, and your opponent will know that you have that move and either switch to a faster Pokemon or use a move that is not very effective against itself.
Answer is no, Me First is a useless move will poor distribution, most Pokemon being able to use it are too slow or too frail. Lucario is a Pokemon that is too frail to be using a gimmicky move like this, it has far better options for its moveset than Me First.
Lucario @ Life Orb
Ability: Justified
EVs: 252 Atk, 252 Speed, 4 HP
Nature: Adamant
Bullet Punch/ Extreme Speed
Close Combat
Crunch/ Ice Punch
Swords Dance
OR
Lucario @ Life Orb
Ability: Justified
EVs: 252 Sp. Atk, 252 Speed, 4 HP
Nature: Modest
Dark Pulse
Aura Sphere
Hidden Power Ice/ Psychic
Nasty Plot
Source
Link