Why are people even discussing banning these two? Aren't we not supposed too? Ok, I do agree that Mega Latias will be, but I don't think Mega Latios will be, but that's not something really to be discussed. Anyways, I'd like to say that Physically Defensive M-Latias is wholy shit good, like look at this:
252+ Atk Life Orb Bisharp Sucker Punch vs. 252 HP / 252+ Def Latias: 234-276 (64.2 - 75.8%) -- guaranteed 2HKO
But, I do feel, to be able to withstand Bisharp, it should run Hidden Power [Fighting]:
0 SpA Latias Hidden Power Fighting vs. 0 HP / 0 SpD Bisharp: 312-368 (115.1 - 135.7%) -- guaranteed OHKO
Also, if it doesn't run Life Orb:
252+ Atk Bisharp Knock Off vs. 252 HP / 252+ Def Latias: 146-174 (40.1 - 47.8%) -- guaranteed 3HKO
252+ Atk Bisharp Sucker Punch vs. 252 HP / 252+ Def Latias: 180-212 (49.4 - 58.2%) -- 98% chance to 2HKO
That's just crazy. I'd really love to run Psyshock / Hidden Power [Fighting] / Calm Mind / Roost, as it is one of the few Megas that don't mind no Leftovers. Look at this power:
+1 0 SpA Latias Psyshock vs. 252 HP / 252+ Def Blissey: 313-370 (43.8 - 51.8%) -- 71.9% chance to 2HKO after Stealth Rock and Leftovers recovery
+2 0 SpA Latias Psyshock vs. 252 HP / 252+ Def Eviolite Chansey: 306-360 (43.4 - 51.1%) -- 98.8% chance to 2HKO after Stealth Rock
It needs +2 to break through Chansey, but it should have no problem getting there. Here are some more moves it doesn't mind taking:
252 Atk Krookodile Knock Off vs. 252 HP / 252+ Def Latias: 126-150 (34.6 - 41.2%) -- guaranteed 3HKO
252+ Atk Conkeldurr Ice Punch vs. 252 HP / 252+ Def Latias: 122-144 (33.5 - 39.5%) -- guaranteed 3HKO
252+ Atk Choice Band Talonflame Brave Bird vs. 252 HP / 252+ Def Latias: 150-177 (41.2 - 48.6%) -- guaranteed 3HKO
252 SpA Life Orb Protean Greninja Ice Beam vs. +1 252 HP / 4 SpD Latias: 151-182 (41.4 - 50%) -- 0.4% chance to 2HKO
252+ Atk Choice Band Huge Power Azumarill Play Rough vs. 252 HP / 252+ Def Latias: 338-402 (92.8 - 110.4%) -- 56.3% chance to OHKO
252+ Atk Aegislash-Blade Shadow Sneak vs. 252 HP / 252+ Def Latias: 102-122 (28 - 33.5%) -- 0.2% chance to 3HKO
252+ SpA Aegislash-Blade Shadow Ball vs. +1 252 HP / 4 SpD Latias: 152-180 (41.7 - 49.4%) -- guaranteed 3HKO
252 SpA Mega Charizard Y Fire Blast vs. +1 252 HP / 4 SpD Latias in Sun: 74-87 (20.3 - 23.9%) -- guaranteed 5HKO
252+ Atk Cloyster Icicle Spear (5 hits) vs. 252 HP / 252+ Def Latias: 240-280 (65.9 - 76.9%) -- guaranteed 2HKO
252+ Atk Dragonite Dragon Claw vs. 252 HP / 252+ Def Latias: 186-222 (51 - 60.9%) -- guaranteed 2HKO
252 Atk Mega Garchomp Outrage vs. 252 HP / 252+ Def Latias: 306-360 (84 - 98.9%) -- guaranteed 2HKO
252 SpA Gengar Shadow Ball vs. +1 252 HP / 4 SpD Latias: 122-146 (33.5 - 40.1%) -- guaranteed 3HKO
252+ Atk Mamoswine Icicle Crash vs. 252 HP / 252+ Def Latias: 194-230 (53.2 - 63.1%) -- guaranteed 2HKO
252+ Atk Teravolt Kyurem-B Outrage vs. 252 HP / 252+ Def Latias: 336-396 (92.3 - 108.7%) -- 50% chance to OHKO
252 Atk Life Orb Weavile Ice Punch vs. 252 HP / 252+ Def Latias: 195-229 (53.5 - 62.9%) -- guaranteed 2HKO
Ok, by now this is just becoming a wall of text, so I'll stop it here. But as you can see, it can handle very many hits and is bulky as fuck.