|This build aims to capitalize on Innes's great natural Spd and solid Atk/Def to become a player-phase powerhouse that can also be tough to take out on enemy phase given his high Spd and Def.
Brazen Atk/Def 3 is the go-to A-slot skill, and since it is available from 4* Ares it shouldn't be too tough to come by. Combined with a +Def refined weapon, this puts Innes's Def near or above 40 and Atk around 55 when under 80% HP (boosted slightly higher by initiating, if using Beach Banner+). That combined with mid-40s Spd makes him all but invulnerable to physical attackers without effectiveness and/or color advantage. Fury 4 can be used as a little more accessible alternative.
Desperation 3 is your ideal B-slot skill, capitalizing on his mid-40s Spd to double most enemies and comboing with Brazen Atk/Def 3 to make him frightening below 75% HP.
C-slot skill depends on what type of team you are planning to run him on. His default Goad Fliers is good for flying teams and Tactics skills are great for non-emblem teams. His Res is not high enough for Ploys, nor is his HP high enough to be reliable in the case of Panic Ploy. Threatens can be okay, but are usually outclassed by team buffs.
Speed +3 (or another Spd-boosting seal) is a great option to bump his Spd to the next level. Another option is running a +Spd refined weapon, which would drop some raw Def but allow flexibility in the Seal slot.
Lastly, Bonfire is the most obvious special choice to take advantage of his great Def (while boosted) while still having a low enough cooldown to hopefully fire one off in a round of Desperation combat. Fully Def-boosted, this will hit for 20+ damage on top of his ~55 Atk, leaving most enemies scorched.