Does Focused on the Kill require your team to be a Merc? or could you use it with IG-88 added to an Imperial list via Temporary Alliance? Since its an attachment my initial reaction was that you could use it on IG wherever he appears, however the card has the Merc symbol on it unlike some of the other attachments from this wave.

Temporary Alliance does not allow to take skirmish upgrades. You can only use the skirmish upgrades of your of affiliation.

You can only include Focused on the Kill in a mercenary army.