Metamagic cheese in E6

[HMS Invincible]

Saying that +0 metamagics don't get reduced to -1 by Arcane Thesis (or any other reducers) and "cap out" at a reduction of +0 should work. Another house rule I've read about (but not tried) goes further and specifies that metamagic reducers cannot be applied to more than one metamagic feat per casting.

That's avoiding the question. Of course I can house rule it. What I really want to know is this:
I cast a generic spell with arcane thesis. It's a

Spoiler: Metamagic Arcane Thesis +0 3rd level

Show

Alternative Source Spell (Dragon #325): For the cost of 1 caster level, and one slot from a class that grants the spell, you can prepare an arcane spell as divine, or a divine spell as arcane.
Black Lore of Moil (Complete Arcane, page 76): Any Necromancy spell deals +1d6 damage, +1d6/two spell levels. Must expend a 'runebone' that costs 25gp per 1d6 to be generated. See feat for full details.
Born of Three Thunders (Complete Arcane, page 76): Any [electricity] or [sonic] spell that deals damage has its damage split split 50/50 between electricity and sonic damage. Adds Fort save or deafened, plus Reflex save vs being knocked prone.
City Spell (Cityscape, page 59-60): Any spell with an energy descriptor and cast within any urban area above the size of small town converts 50% of its damage into "city" damage.
Cooperative Spell (Complete Arcane, page 77): Requires additional person with this feat, who casts the same spell with you. Adds +2 DC and +1 caster level to beat Spell Resistance, and uses the better of the two spellcasters' DC and caster level. Can be expanded into multiple extra people, adding +1 DC and +1 CL for each additional person.
Energy Affinity (Miniature's Handbook): Subsumed by Energy Substitution; also slightly harder to qualify for. Same effect.
Energy Substitution (Complete Arcane, page 79): Any spell with an energy descriptor can be changed to have the energy descriptor (and deal corresponding damage type) chosen by this feat.
Ghost Touch Spell (Ghostwalk, page 34): Allows spells to affect ghosts and only ghosts.
Imbued Healing (Complete Champion, page 60): Adds a rider effect specific to one of your domains on the tail-end of your conjuration (healing) spells. Has a table for non-PHB domains on page 53.
Invisible Spell (Cityscape, page 61): Removes all visual manifestation of a spell.
Lord of the Uttercold (Complete Arcane, page 81): Any spell with the [cold] descriptor can be changed to deal half cold damage, half negative energy damage.
Miser With Magic (Kingdoms of Kalamar Player's Guide, page 88): Not really a metamagic feat, despite being marked as such. After casting a spell, make a Spellcraft check at a DC = 10+(2* Spell Level). Succeed, and you get the spell back. Fail by 5 or more, you don't cast it and lose the slot. Regains a number of spell levels equal to your primary casting stat modifier.
Sanctum Spell (Complete Arcane, pages 82-83): Has an effective spell level of +1 when cast in sanctum, but -1 cast outside of sanctum.
+1
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Bend Spell (Dragon #291, Dungeon Compendium Vol. 1): Negates cover bonuses.
Blistering Spell (Player's Handbook II, page 91): +2 fire damage per spell level, and -2 to attack rolls and checks if the target fails its save. [fire] spells only.
Clawed Spell (Dragon #315): Spell deals 1d6 Force damage for every 5 caster levels.
Coercive Spell (Drow of the Underdark, page 47): Spell deals a -2 penalty to Will saves for 3 rounds, non-cumulative.
Consecrate Spell (Book of Exalted Deeds, page 42/Complete Divine, page 79): Spell gains [good] descriptor, and if it deals damage, half of it is divine damage.
Corrupt Spell (Book of Vile Darkness, page 47/Complete Divine, pages 79-80): Spell gains [evil] descriptor, and if it deals damage, half of it is divine damage.
Deafening Spell (Drow of the Underdark, page 49): Any spell that deals damage also deafens its target for 1 round. No save.
Deceptive Spell (Cityscape, page 60): Makes a spell appear to originate from a different direction.
Energize Spell (Libris Mortis, page 26): Deals 1.5x damage to undead creatures, but 0.5x damage to non-undead and objects.
Enlarge Spell: Doubles the Range entry on a spell's description.
Extend Spell: Double duration of a spell.
Fell Energy Spell (Dungeon Compendium Vol. 1, Dragon #312): Any spell that gives a numerical bonus gives an extra +2 to undead.
Fell Weaken (Libris Mortis, page 27): Any spell that deals damage also deals out a non-cumulative -4 Strength penalty.
Fiery Spell (Sandstorm, pages 49-50): Only usable on spells with the [fire] descriptor, adds +1 damage per die of damage dealt by the spell.
Flash Frost Spell (Player's Handbook II, page 91): Only usable on spells with the [cold] descriptor, adds +2 damage per level of the spell and creates a quasi-grease effect in the spell's area for 1 round. Note that any spell when using the Snowcasting feat is a [cold] spell.
Forceful Spell (Dragon #358): Adds a Save-or-Suck to any spell on any one target (even on an area-of-effect spell): Save or be knocked prone and stunned for 1 round.
Imbued Summoning (Player's Handbook II, page 92): Any creature created by conjuration (summoning) spells can have any spell you know of 3rd level or lower with a range of touch cast on it auto-magically.
Sculpt Spell (Cityscape, page 63, Complete Arcane, page 83): Changes an area spell's area.
Silent Spell: Removes Verbal components.
Still Spell: Removes Somatic components (and arcane spell failure for armor).
Transdimensional Spell (Complete Arcane, page 84): Allows a spell to affect an incorporeal creature, creatures on the Ethereal Plane or Plane of Shadow, and creatures within an extradimensional space within the spell's area.

Insert favored spell

Tell me why that spell I just casted is playable in E6. Note I didn't even bother to pick a SR: No spell.
Note2. Edit for people that are pedantic.