Still need Nullify on Haar. He'll be instrumental for speeding us along.
Crossbow to your Sniper. Boyd won't need it this time around, and if your chosen Sniper is Rolf, he'll need the dissuasion effect if your party gets flanked by one of the Dragonmasters.
How's Ike's Spd? Is he close to 27? IF his Str and Skl are capped, you can try to BEXP his Spd up. If not, you'll likely get HP, Str/Skl, and Def. If they aren't capped, try pulling Ike up a level or so and then set him up with Blossom (and 95 exp or so). If you transferred the Speedwing from the Royal Knights to Haar/Neph/Brom/Heather in P2-E, you can also use that. If Ike's Spd is less than 27, the BK battle is still salvageable, but you better have prepped for it. More on that later.
Boss Type: Triggered. Micaiah (and all of the DB for that matter) moves when approached.
Speed is your primary concern, so everything that keeps your units moving is a good thing. Gatrie is good to bring along, if to do nothing more than Shove other units farther along.
Haar can move freely across this map. He can pick off Sages (to clear the way for Ranulf), or Dragonmasters (to preserve Mist and Reyson).
Recruit Ulki and Janaff (you only have to talk to one of them). I prefer to do this with Reyson, to keep Ike and the front line moving forward. From that point on, they can help guard against Dragonmasters or Shove other units along (only when shifted).
To optimize Ike's chances of survival against the BK, he needs to raise his evasion as high as possible. Consider:
A solid, high-rank support. Ike already has Earth affinity, but he can push his evasion higher by stacking it with a Dark (Soren) or Wind (Ranulf, Rolf) affinity. EarthxEarth is out of the question since Oscar can't help you here.
Biorhythm. Right before the battle (on turn 11 or 12, most likely), Reyson can use Bliss on Ike.
Terrain. There is a thicket in the gap between islands, adding another 10 avoid.
In this run, Ike had 26 Spd and survived easily, dodging the BK twice at ~40% hit chance.
If you're going for the Soren-Micaiah battle and conversation, Soren will need one of two things: Meteor/Bolting, or a ride with Ulki/Janaff/Haar. If you can't do it via siege tome, then Soren should not be Ike's support option. For the siege tomes:
Bolting - obtainable by Disarming the Sage in the northeast corner of P3-2. A rare drop.
Meteor - obtained by two methods: transferring Calil's to the Mercs via Haar/Neph/Brom/Heather at the end of P2, or by Disarming the Sage in the southeast corner of P3-5. The first is the easier option.
Honestly, if you can manage it, siege tomes are the better option.