Way to remove level requirement to Oblivion’s quests

From the Oblivion Wiki:

Some magical effects can increase your skill above 100, but in general increases above 100 have no real effect. The only exceptions are Acrobatics and Athletics , which will continue to increase your character's jump height and run speed, respectively, up to a maximum value of 255.

As for attributes:

The current value of an attribute can be boosted past 100, and many, but not all, benefits of the attribute continue to increase for values greater than 100 (see Magical Effects on Attributes ). Most aspects of game play are based upon the current value of the attribute.

Fortifying an attribute temporarily raises that attribute's value by M points, for a period of D seconds. Fortify Attribute can increase an attribute above its base value and can even increase an attribute above the maximum value of 100. Increases in attributes past 100 have the same effect as below 100 with one exception: weapon damage. Luck's effect on other attributes of +5 Luck = +2 (Other Attribute) is not altered when Luck is above 100; however, as it effectively raises the level of other skills up to a cap of 100, Luck has a diminishing effect on attributes that exceed the cap, and ceases to have an effect on attributes that reach 100. See Oblivion:Luck and the other attribute pages for details of their effects on skills.

So while fortifying endurance past 100 will boost your health, fortifying strength past 100 will not boost your melee damage but it WILL continue to increase the maximum carry weight and fatigue.

That's sort of how it works. From the Oblivion FAQ:

When you level you get to raise the values of three attributes. The amount you can raise an attribute by depends on how many skill points you have gained in skills governed by this attribute (major and minor).

0 skill points grants a +1 bonus
1-4 skill points grants a +2 bonus
5-7 skill points grants a +3 bonus
8-9 skill points grants a +4 bonus
10 or more skill points grants a +5 bonus

It is never possible to gain more than a +5 attribute bonus when leveling up. Attribute bonuses not used at one level (or surplus points past 10 in the skills governed by an attribute) do not roll over to the next level.

For example, say a character has the following major skills (seven in total, listed by attribute):

Agility: None
Endurance: Armorer
Intelligence: Conjuration; Mysticism
Personality: Illusion
Speed: None Strength: Blade
Willpower: Destruction; Restoration

Since his previous level-up he has increased some skills (see below, increase in parenthesis after each skill). When he acquired the 10th increase in a major skill, he qualified for a level-up. The attributes offered to him would be as listed to the right in the examples below.

Example 1
Attribute Skill Increases Bonus
Agility Security (2) +2
Endurance None +1
Intelligence Alchemy (10), Conjuration (1), Mysticism (1) +5
Personality None +1
Speed Athletics (5), Acrobatics (5) +5
Strength Blade (4), Blunt (4) +4
Willpower Destruction (4) +2

For those concerned with over-leveling or skill management this is not a "perfect" level-up. An example of a 5/5/5 increase (as mentioned in Efficient Leveling) for this character could be:

Example 2
Attribute Skill Increases Bonus
Agility None +1
Endurance None +1
Intelligence None +1
Personality Illusion (6), Mercantile (4) +5
Speed Athletics (5), Acrobatics (3), Light Armor (2) +5
Strength None +1
Willpower Destruction (4), Alteration (6) +5

Here only 3 attributes have more than the minimum +1 modifier, and they all get the maximum +5. Illusion and Destruction are the only major skills that have been increased (4+6=10), along with a total of 20 minor skills. No skills have been over leveled. Note that the last one of the increased skills has to be a major skill.