Just no to special Luke. The same shortcomings to physical Luke still apply with no real benefits: impossible to set-up, priority is underwhelming (for sweeping), still walled by standard Uber defensive Poke, etc. Additionally, Aura Sphere is significantly weaker than Close Combat (180 vs. 240 base power after Adaptability in addition to the slightly higher Atk. stat) to the point that certain Adamant E-Killer may not be OHKO'd, and you lose the ability to BP weakened Xerneas to death, major selling points for Luke's use. I would explain further, but I feel numbers would be more useful for this purpose:
252 Atk Adaptability Mega Lucario Close Combat vs. 252 HP / 252+ Def Groudon: 162-192 (40 - 47.5%) -- guaranteed 3HKO after Leftovers recovery
252 SpA Adaptability Mega Lucario Aura Sphere vs. 252 HP / 0 SpD Groudon: 202-238 (50 - 58.9%) -- 71.9% chance to 2HKO after Leftovers recovery
252 Atk Adaptability Mega Lucario Iron Tail vs. 252 HP / 252+ Def Giratina: 150-178 (29.7 - 35.3%) -- guaranteed 4HKO after Leftovers recovery
252 SpA Adaptability Mega Lucario Flash Cannon vs. 252 HP / 6 SpD Giratina: 158-186 (31.3 - 36.9%) -- guaranteed 4HKO after Leftovers recovery
252 Atk Adaptability Mega Lucario Close Combat vs. 200 HP / 0 Def Arceus: 488-576 (113.2 - 133.6%) -- guaranteed OHKO
252 SpA Adaptability Mega Lucario Aura Sphere vs. 200 HP / 0 SpD Arceus: 316-376 (73.3 - 87.2%) -- guaranteed 2HKO
252 Atk Adaptability Mega Lucario Iron Tail vs. 252 HP / 176+ Def Lugia: 150-178 (36 - 42.7%) -- 95.2% chance to 3HKO after Leftovers recovery
252 SpA Adaptability Mega Lucario Flash Cannon vs. 252 HP / 80 SpD Lugia: 120-142 (28.8 - 34.1%) -- 98.9% chance to 4HKO after Leftovers recovery
The list goes on... but overall, you're hitting only marginally or not even harder with Special Luke; the only main upside is the Flash Cannon accuracy advantage over Iron Tail (which I admit, I cannot ignore... da hax).
Anyway, for lol's in actual battles I've played, I couldn't resist:
252 Atk Arceus Earthquake vs. 0 HP / 6 Def Mega Lucario: 228-270 (81.1 - 96%) -- guaranteed 2HKO
252+ Atk Choice Band Teravolt Zekrom Outrage vs. 0 HP / 6 Def Mega Lucario: 198-234 (70.4 - 83.2%) -- guaranteed 2HKO
Those surprised (and angry) comments by my opponents...