On the subject of Latias fitting into the metagame, a support set like this might work:
 
Latias @ Leftovers
Levitate
Bold Nature
EVs: 252 HP/60 Def/108 SpA/32 SpD/56 Spe
~Wish/Recover
~Surf
~Thunderbolt
~Psychic/Grass Knot/Dragon Pulse/Protect/Calm Mind
 
The healing move prolongs lifespan, and should be chosen based on whether you want Latias to be a team player, or a counter. Personally though, I'd go for Wish.
 
Surf hits Heatran hard, and Latias makes a great counter to Heatran unless he's stuck on Dragon Pulse with Specs (although unspecs Dragon Pulses will 3HKO). Grass Knot could be used in its place, but I think that Latias is such a great Heatran counter with Surf it's a shame to waste it. Thunderbolt is mainly for Gyarados and bulky Waters that try to come in and wall Latias whilst firing off Ice Beams. She can easily take Ice Beams despite their Super Effectiveness, taking at most 44% from the standard 299 SpA Timid Starmie. The final move is for coverage; Psychic hits Heracross and other fighters hard, and it's useful for Machamp. Grass Knot hits T-tar, Hippo and Donphan harder than Surf and many bulky Waters harder than T-bolt, although with Surf and T-bolt its coverage is inferior. Dragon Pulse provides Latias with an attack to hit everything neutral with, as nothing resits Water/Electric/Dragon except Shedinja. Protect deserves a mention because it allows you to heal with Wish. Calm Mind also deserves a mention, but in general a sweeping set with more Speed would be more suited to Calm Mind's stat upping graces.
 
The EVs are quite specific. Max HP helps take the most hits. 60 Defence EVs garuntees that a once-DD'd Gyarados will never 2HKO with Stone Edge, which is its most powerful option against Latias barring Ice Fang. 108 Special Attack EVs is needed to garuntee the OHKO against 4 HP/0 SpDef Gyarados with Thunderbolt, and it gives the rest of her attacks more bite as well. 56 Speed hits the magic 270 mark; just ahead of Heracross. The remaining 32 EVs are in Special Defence to help take weak Ice Beams and the like. 
 
Latias is a good counter to several top tier threats, which is what I tried to go for here. This particular Latias is a great counter to your standard Gyarados, Heatran, Heracross (-Megahorn), Infernape, Starmie and Bulky Waters/Grounds. However, it can't counter some of the very biggest threats in Tyranitar and Salamence. The same sort of set can work on Latios, but Latias is bulkier and gets Wish.