Kunimatyu said:
If simplicity is your goal, how about only having higher level spells (ie. level 4+ spells) as scrolls that have to be found, or require a (titan/deity/outsider) to make them for you? That way, higher-level magic is present but rare, relics of a forgotten age, not something casually thrown around every encounter.
If you allow wizards to cast disintegrations, walls of force, et al several times per day, not only will every single PC be tempted to take 1 level of wizard just to get all of that(and taking the feat ten times to get 6th level spells really isn't that hard in E6), but you'll completely wreck the balance of your game, and lose the flavor of E6 -- you'll just have "lower level D&D that doesn't work and has a really high death rate".
I'm not trying to be negative here, and I can certainly understand the desire for simplicity, but I'm afraid your solution will result in a wrecked campaign, so I'm trying to give the best advice I can.
If you look at the feat again, you'll notice it can only be taken a maximum of 5 times. The highest level spellcaster in the campaign will only be equivalent to an 11th level Wiz, minus the attendant hp, saves, bonus feats, etc. And unless they somehow get their Int up to a 22, you're looking at a max of 1 6th lvl spell a day for the most powerful Wiz in the campaign (2 for a specialist). And of course, that Wiz will be shy 5 feats of metamagic, toughness, etc.
Here's an NPC, 6th level plus 10 feats (50,000 xp):
Gansley, Elf Fig4/Wiz2, AC17, hp37, CG, Atk melee+8 (longsword+1, dmg1d8+3) ranged+10(longbow, dmg1d8), Init+7, Move30’, Fort+4 Ref+6 Will+4, Str13, Dex16, Con11, Int15, Wiz10, Cha11; Skills Jump+8, Climb+8, Intimidate+6, Spot+5, Search+3, Hide+8, Spellcraft+4, Concentration+8; Feats Weapon Focus(longsword), Weapon Specialization (longsword), Advanced Magic (x3), Armored Casting, Combat Casting, Skill Focus (Concentration), Improved Initiative, Extend Spell, Lightning Reflexes, Improved Initiative, Point Blank Shot, Weapon Focus(longbow), Empower Spell, Toughness;
Equipment +1 Longsword, Elven Cloak, Elven Boots, MW Longbow, MW Chain Shirt, Wand of Flaming Spheres (CL5).
Spells (4/4/3/1): 0-mage hand, prestidigitation, light, detect magic; 1st-sleep, charm person, true strike, floating disk; 2nd- levitate, knock, shield(extended); 3rd- Displacement.
Hardly a campaign wrecker, especially not next to the raging 6th level barbarian with 2 attacks per round!
