I'll add things to this post as I think of them. Feel free to veto things as desired.
Minato Arisato
Standard bluelike interps apply. Nothing special here.
Meliadoul Tengille (FFT: WotL)
War of the Lions specifically lets her break skills work on things without applicable equipment and gives her a damage boost on them as well - Shellbust Stab does PA*(WP+5), Blastar Punch PA*(WP+4), Hellcry Punch PA*(WP+3) and Icewolf Bite PA*(WP+2).
Setup: Level 40 assumed. Divine Knight job at all times. Can set any secondary command set she wishes (including WotL Dark Knight) with all abilities learned. Reaction ability and Movement ability are locked to MP Switch and Move-MP UP, respectively, but she can set any Support ability she wishes (including the Dark Knight ones). Dark Knight stuff will be listed below since it's not covered in the existing stat topics. She can have 97 Brave and 94 Faith, too.
Equips: For this tourney, she gets access to everything in FFT, accessories and WotL multiplayer gear (which in the iOS version is storebought in aftergame) included. In practice, this means:
Weapon - Chaos Blade (40 WP, Always: Regen, Inflict: Stone) is the obvious go-to. If she's not using the Brigand's Gloves and needs the speed, she can fall back to Excalibur, of course.
Shield - Escutcheon II (75 P-EV, 50 M-EV) is the obvious choice. Some setups, in theory, could see use for the Reverie Shield (50 P-EV, 25 M-EV, Half: all elements), though.
Head - Grand Helm (150 HP, Immune: Blind/Sleep) would be her default. She can use Vanguard Helm (150 HP, 20 MP) with MP-sucking secondaries or if she wants a bit of extra MP Switch buffer, or even Ribbon (10 HP, Immune: all negative status but Chicken/Oil/Innocent/Faith) if she wants the status protections.
Body - She has the most good options here:
Mirage Vest (120 HP, Immune: Stone/Poison/Sleep, +1 Speed) is probably her default of choice due to the +Speed.
Minerva Bustier (120 HP, Immune: Fire/Lightning/Wind/Darkness, Half: Ice/Water/Earth/Holy)
Grand Armor (170 HP, Always: Reraise/Regen) - the Reraise does her no good in the DL, but the Regen might if she doesn't need the other things.
Secret Clothes shouldn't be forgotten either, of course (don't have the stats on them handy atm).
Accessory - The most prominent choices among WotL-specific accessories would be:
Brigand's Gloves (Speed +1, Always: Haste) - Probably the default, due to the +Speed and alternate source of Auto-Haste.
Sage's Ring (Absorb: Fire/Ice/Lightning/Wind/Water/Earth/Holy/Darkness) - Yes, really
Empyreal Armband (Speed +1, Immune: Slow/Stop/Immobilize)
Tynar Rouge (PA +3, MA +3, Always: Protect/Shell/Haste) - If she doesn't actually need the extra speed point, this is better than the Brigand's Gloves.
Relevant things from the WotL Dark Knight:
COMMAND SET - DARKNESS
Sanguine Sword: (PA*WP)*.8 HP drain, no element.
Infernal Strike: (PA*WP)*.8 MP drain, no element.
Crushing Blow: PA*(WP+2) damage, carries weapon's element, 25% chance to inflict Stop.
Abyssal Blade: PA*(68/100)*(WP+3) damage, carries weapon's element, costs HP equal to 20% of max HP.
Unholy Sacrifice: PA*MA*(68/100)+(MHP/3) damage, Dark element, 25% chance to inflict Slow. Costs HP equal to 30% of max HP.
SUPPORT ABILITIES:
HP Boost: Boosts maximum HP by 20%.
Vehemence: Boosts damage done, healing done, and damage taken by 50%.
Ryu (Breath of Fire III)
Standard DL setup, with three exceptions:
One, he gets apprenticed to Meryleep at level 18 and stays on her for the rest of the game. This gives him -22 HP, -22 Pwr, -20 Def, and +44 Agl from his normal DL stats (as per Dhyer's topic). He also gains War Shout (MT attack power buff for 6 AP) and Shadowwalk (automatic critical hit for 8 AP) in his skillset.
Two, he gets to use a single Manly Clothes each fight if desired.
Three, he can also use whatever stat-boosting accessories he likes.