Reina, when? Weird thing is that as a playable unit, her bow rank is lower than her lance rank while as an enemy, it's even or higher on Lunatic apparently. On that note of a flying archer, I kind of wished that there was a bow-wielding wyvern rider. Don't know why other than it would be cool.
Boyd, Geitz, or any high defense archer would be useful right now. Gordin's the only one with high defense while on the other side, Faye, Niles, and sort of Rebecca have high resistance, and everyone else has average defense or resistance. So, if you really need a high defense archer for whatever reason, you're kind of screwed while you have 3 options for high resistance.
They could do a bow knight Selena based on her class an enemy in Birthright. Her current stat spread could be fine, but that would mean she'd have the highest BST of not just archers (154 with Faye), but mounted units (155 with Eliwood -- not sure about Camus or Xander yet). Still, she doesn't do a lot of damage to begin with as being colorless means she no longer has T-Adept or a gem weapon to boost her attack and she'd just be the tanky archer which is fine. If need be, they could just deduct 2-3 points from her defense since Bow Knights have lower defense caps than Heroes in Fates. Cavalry buffs, though... Main reason why Olwen is better on a team compared to Reinhardt who does well on and off-team, but not really good on teams like his sister.
No, I meant that you -- pretty sure it was you -- sacked a Setsuna to give M!Robin so he could destroy Takumi. All I could do was sit in silence...
The Brave Bow and Brave weapon builds I've seen on Serene's Forest don't use Vantage, instead, Desperation is used. Paired with Life & Death and either Ardent Sacrifice or Reciprocal Aid to drop down into Desperation's range and you can double with a Brave weapon provided your speed is high enough which is why Jeorge, Klein, Setsuna, and Takumi are candidates for the Brave Bow, L&D, and Desperation build with Takumi, unsurprisingly, being the best at it. Rebecca's in a weird spot where her slightly higher attack than Setsuna, but lower speed makes it not great on her since she doesn't do enough damage unlike Jeorge and Klein who are slower than her by a bit. If not, then a different B-slot is used like Drag Back or Hit and Run to get out of range after a kill which is what Donnel's default build demonstrates and only works for melee units.
The issue with Vantage is that it's not considered initiating combat; it's just that it switches the turn order around, so, if Lon'qu is attacked, then instead of attacking after his opponent, he attacks first, then his opponent if they're still alive, and if he can double, then he attacks again if he's still alive. Basically, it means that you only hit once with a Brave weapon instead of hitting twice per hit.
That said, Vantage can work to ensure you hit first to survive by hopefully killing your opponent first. Similar case with Quick Riposte which lets you counter every time you're hit, so Brave weapon's -5 speed penalty can be mitigated by that. Still, you might want to use something else and in Setsuna's case where her attack and defenses are low, Vantage might be better with a different bow or she should just avoid it by running a Desperation build to double with Brave Bow.
Edit: Virion with a Brave Bow was mentioned somewhere, but I don't remember where. He's just going to have a different build is all.