This has a similar concept to my March of the Ents deck. Use The Eagles Are Coming! to get as many eagles into your hand and therefore into play as quickly as possible. Like Entmoot, The Eagles Are Coming! shares the same trait as the allies it is retrieving, so with a little luck we may be able to use more than one in the same round. For this purpose, I would really be looking for at least one copy in my opening hand.
Gandalf should use a Word of Command to help retrieve our other roaming wizard, Radagast; who should be brought into play to help pay for eagle allies and keep them alive if needs be. His next Word should find Song of Battle to make the most of Pippin's resources in this heavy deck. The final copy should be used to find any of the wizard's various attachments that might be proving illusive (Narya is priority.
Eagles of the Misty Mountains should be played as early as possible in order to make the most of other allies leaving play. The main strategy is to get multiple copies of Support of the Eagles on Merry in order to make him a formidable attacker/defender. All copies of Fast Hitch should therefore also go on him as it will enable him to attack multiple times each round. If Merry gets his attachments quickly enough, it may not be necessary to get the Eagles into play as we won't need to attack with and discard Vassal of the Windlord (as we can just add its to Merry's).
If his attachments allude us for too long though, we will end up having to attack and defend with eagle allies in which case we will likely see the Vassals and Winged Guardians leaving play and therefore it is best to strengthen the Eagles with these cards, so that Merry only needs the Support of one ally to become a decent attacker/defender. If the Eagles take there time to arrive (as they always do in the books) then To the Eyrie can safeguard against the permanent loss of an ally in the early game and Gwaihir can be used for the same purpose.
This deck is weak against shadow effects, so it might be best to only use Merry to defend against non-unique enemies and have Gandalf use his Staff to discard its shadow card before it is turned, particularly in quests where the shadow effects prevent the defender using their . Otherwise, it would probably be better to use eagle allies to defend and reserve Merry for attack. However, if the worst does happen and Merry is defeated, Landroval can be used to bring him back from the brink (provided that Pippin is able to help pay for cards at that point. A pipe on both wizards will certainly mean that Gandalf should be able to pay for cards of any sphere most of the time and with Narya in hand he can always Sneak in Landroval to make use of his action. I have also included a copy of Second Breakfast to return an attachment to Merry in this instance, although it will probably be best to reserve a spare of both Support of the Eagles and Fast Hitch in case Merry is defeated.
Update: after testing this deck, I would have to say that it would work better in multiplayer as it takes some time to get everything set up due to the expense of many of the cards. I would recommend a quest heavy support deck that focuses on location control and treachery cancellation and to bring in some threat reduction.