
First of all you can make an effort to baton pass an agility to him. The real problem with this is that despite the ease of doing this, flareon can't really stand an attack after that (Possibly if he resists it or its a non-super effective special attack). This can be remedied by using some sort of sleep move, or encore but this takes longer to set up and doesn't function very well. In this particular situation Flareon would have to use a ev spread that looks something like this:

Flareon@Life Orb
Adamant
31/31/31/31/31/31 (Rather unrealistic)
134 hp/ 252 atk/ 124 spe (with an agility this will outspeed anything that isn't scarfed other than nijask)
Then comes the moveset which also is another reason why flareon is UU, There is practically nothing that it can use to abuse its extremely high attack. It's best two attacks being return and fire fang. Bite can cover other typing, Quick attack/Rock Smash/Iron tail/ Giga impact can go in the last slot but quick attack is probably your best bet if you can't pull off the agility.
The second option for trying to increase flareons usefulness in the metagame would be a choice scarf, The moveset would look pretty much the same but the EV's would have to be max in speed to pull it off not to mention the need for a +Spe nature.

Flareon@Choice Scarf
Jolly
6 hp/ 252 atk/ 252 speed
Return
Fire Fang
Iron Tail
Bite
No need for quick attack in this set as you should outspeed most non-scarfed opponents anyways.
Anyways, thoughts?
tl;dr
Flareon can succesfully take a pass from an agility and fair pretty well, or maxamize its speed with a choice scarf.