I mapped out some of the more viable suggestions that looked like they needed more concrete explanations:
Serge (w/ White elements, no Lynx)
Chrono Cross
Floor 1:
Photon Ray x2 *Lv1 White attack spell
Floor 2:
Photon Ray (storebought)
Revive x2 *Revival + 25% healing
Turn White x1 *Gives opponent innate resistance to White, weakness to Black
Meteorite (storebought) *Lv2 White attack spell
x5WhiteOut (storebought) *ITEM, heals Blind, godly.
RecoverAll x1 *MT Heal (Unsure of percentage, says 'Medium')
(SERGE TECH) Dash&Slash x1
Floor 3:
Photon Ray (storebought)
Revive x2
Turn White x1
Meteorite (storebought)
x5WhiteOut (storebought)
RecoverAll (storebought)
Anti-Black x1 *ST, Seals use of all Dark-elemental skills/spells
MeteorShower x1 *Lv4 White attack spell
(SERGE TECH) Luminaire x1
Floor 4:
Photon Ray (storebought)
Revive x3
Turn White (storebought)
Meteorite (storebought)
x5WhiteOut (storebought)
RecoverAll (storebought)
Anti-Black x1
PhotonBeam (storebought) *Lv3 White attack spell
MeteorShower (storebought)
Purify (storebought) *Heals all negative status
x5Panacea (storebought) *ITEM Heals all negative status
StrongMinded (storebought) *Magic Up
WeakMinded (storebought) *Magic Down
Floor 5:
All of the above, plus:
HolyLight x1 *Lv5 White attack spell, MT (also OHKOs Undead)
Magnify (storebought) *Field Effect, all magic deals 1.5x? damage
MagNegate (storebought) *ST, all magic deals 0x damage
Floor 6:
HolyLight x2 (assuming you use a HolyLight trap on Miguel)
FullRevival x1 *Revival with 100% healing
Ultranova x1 *Lv6 White attack spell, MT
(SERGE TECH) Flying Arrow x1
Floor 7:
HolyHealing x1 *MT full healing/status healing
Saints x1 (from the Sky Dragon) *Summon, requires full white field. MT Healing and White Damage
Notes: With Elements, Serge gets some interesting Magic manipulation tricks with Strong/Weak-Minded, plus a Field Effect to increase ALL spell damage by 1.5. MagNegate is an ST Magical invincibility move that he can get from the store. An interesting magical spoiler or great accessory to a magic-heavy team. He also gets decent durability and physical/magical damage. As well as CC accessories. Pretty awesome Heavy/Low Godlike?
Feena:
Grandia
Floor 1: Knife, Whip, Fire
Knifehurl
Randomhurl
Paralyze Whip
Burn
Burnflame
Floor 2: Knife, Whip, Fire; 1 choice of Water, Earth, or Wind
Burn, Burnflame
Burnflare
Fire Whip
If Water:
Heal
Snooze
Alheal
If Earth:
Diggin'
Tremor
WOW!
If Wind:
Howl
Runner
Howlslash
Floor 3: Knife, Whip, Fire; 2 of Water, Earth, or Wind
Burn, Burnflame, Burnflare
If Water/Wind:
Heal, Snooze, Alheal
Howl, Runner, Howlslash
Crackle
Shhh! *inflicts Silence
Crackling
Healer
Fiora *inflicts Moveblock
Zap! Whip
If Water/Earth:
Heal, Snooze, Alheal
Diggin', Tremor, WOW!
Healer
Cure *heals POIZN
Refresh *heals Moveblock
Speedy *Agility up
If Earth/Wind:
Diggin', Tremor, WOW!
Howl, Runner, Howlslash
Shhh!
Zap! Whip
Floor 4: Knife, Whip, Fire, Water, Earth, Wind
Burn, Burnflame, Burnflare
Heal, Snooze, Alheal, Healer
Diggin', Tremor, WOW!
Howl, Runner, Howlslash, Shhh!
Crackle, Crackling, Fiora
Cure, Refresh, Speedy
Resurrect
Halvah
Floor 5:
DragonZap!
Protect *temporary invincibility for one ally
AlHealer+
Floor 6:
Tree of Life
End of the World
Floor 7:
Time Gate
Notes: While Feena may be able to build up the necessary skill levels to -learn- a spell (say Burnflare on Floor 2) by a certain floor, it does not mean she has the MP to use it, or use it repeatedly. Time Gate is, as super pointed out, probably a much later Floor than 7, though I was just throwing the spell to her early. This is just a guideline anyway. If you build her correctly, she can be a potent earlygame assistant and picks up again in Floor 6. Late revival for a healer and not full kind of sucks, though. 2.0-2.5?
Kratos:
Weapon Equips:
Last Fencer Atk 920, Added damage to humans
Excalibur Atk 800, Added damage to humans
Crystal Dagger Atk 750, Acc 30, Added damage to beasts, Small TP regeneration
Laser Blade Atk 710, Atk Light, Added damage to humans
Gladius Atk 620, Acc 20, Added damage to beasts
Ether Sword Atk 590, Added damage to humans
Flame Dagger Atk 530, Acc 15, Atk Fire, Added damage to beasts
Ice Coffin Atk 500, Atk Ice, Added damage to humans
Lightning Sword Atk 470, Atk Lightning, Added damage to humans
Sand Saber Atk 440, Atk Earth, Added damage to humans
Assault Dagger Atk 410, Acc 15, Atk Wind, Added damage to beasts
Aqua Brand Atk 350, Atk Water, Added damage to humans
Silver Sword Atk 265, Added damage to undead
Earth Dagger Atk 250, Acc 10, Atk Earth, Added damage to beasts
Hydra Dagger Atk 220, Acc 10, Atk Water, Added damage to beasts
Steel Sword Atk 160, Added damage to humans
Stiletto Atk 130, Acc 10, Added damage to beasts
Long Sword Atk 85, Added damage to humans
Floor 1:
Demon Fang (base tech)
Sonic Thrust (base tech)
Fire Ball (spell)
First Aid *30% ST Healing
Wind Blade (spell)
Stone Blast (spell)
Floor 2:
Lightning
Double Demon Fang/Fierce Demon Fang (tech)
Air Thrust (spell)
Thunder Blade (spell)
x1 EXGem 1: Strength (Str+5%) or Magical (Wis+5%) or Evasion (Eva+5%) or Appeal (Raise Unison Attack Guage by Taunting, useless)
Floor 3:
Light Spear (tech)
Healing Wind *30% MT Healing
Hurricane Thrust/Super Sonic Thrust (tech)
Eruption
x2 EXGem 1
x1 EXGem 2: Spirits (MaxTP+5%), Vitality (MaxHP+5%), Dash (Faster movement), Personal (Kratos regens HP for the first 10 seconds of each battle, so maybe 3 turns?)
EXSkill "Skill Boost" (Increases skills' TP cost but also power) (uses Magical+Spirits)
Floor 4:
Grave
Lighning Blade (tech)
Hell Pyre (tech)
x4 EXGem 1
x3 EXGem 2
x1 EXGem 3: Slasher (melee combo increases to 6 hits), Turnless (can string skills together in any order), Well Guard (damage incurred while guarding is reduced, useless), Eternal (no effect, but creates cool EXSkill combos)
EXSkill "EX Attack" (increases damage to guarding enemies) (Dash+Personal)
EXSkill "Chivalry" (increases all of Kratos' stats for each additional female in party) (Strength+Slasher)
EXSkill "Healing" (Regen in battle while not attacking)
Floor 5:
Victory Light Spear/Light Spear Cannon (Arcane tech)
Healing Stream *45% MT Healing
x4 EXGem 1
x4 EXGem 2
x2 EXGem 3
x1 EXGem 4: Immunity (fixed probability of avoiding status), Speed Spell (Faster casting times for starter spells), Sky High (airborne melee combo! mostly useless), Spell Charge (use turn to charge a spell, stop before casting, activate as part of a combo, interesting)
EXSkill "Guard Status" (Status immunity) (Eternal+Immunity)
Floor 6:
Demon Spear (Arcane tech)
Super Lightning Blade (Arcane tech)
x4 EXGem 1
x4 EXGem 2
x2 EXGem 3
x2 EXGem 4
Floor 7:
Judgment
Floor 1, his best damage is going to alternate between PhysicalChain->SonicThrust and StoneBlast. On Floors 2 and 3, the magic is clearly stronger, except for possibly against humans opponents towards the end of Floor 3. Floor 4/5 he's lagging and his best damage is vs.Humans with a reordered skill combo. Floor 6 his physical damage picks up again vs.Humans with more combo options. Floor 7, his physical damage is still pretty good and he picks up a good magical damage option, too. From Floor 5 on, he should be making himself Status Immune and occasionally acting as a backup healer. "Chivalry" is an interesting EXSkill and I need to look into how much the stats increase on it.