Handling LA and racial HD in E6

I don't like the idea that characters of races with racial HD can never gain the ability to cast 3rd level spells, or giants can't become spellcasters at all, so I came up with a variant. Please tell me your thoughts.

1. All character (that is, creatures that advance by class levels) can never have more than 6 HD. Tied to the HD are things like hit points, base attack bonus, base save bonuses, skill points, maximum skill ranks, regular feats (at 1st, 3rd and 6th level), and ability increases (4th level).

2. All characters can gain a total of 6 levels in any classes. If they allready have 6 HD because of racial HD, they only gain all the class features that are not tied to HD as defined in 1.

3. Only after a character has a total of 6 levels in any classes, they gain bonus feats for every additional 5,000 XP.

4. Level Adjustment works exactly like in a d20 game. The character is treated as x level higher for determining how many XP he recieves from defeating monsters, and he has to reach the amount of XP x level higher than usual, to get a new level.

The desired effect of this is, that each racial HD and the amount of LA cause the character to have one less feat.

For example, I made a half-elf sorcerer 6 and a lizardfolk sorcerer 6 with the same starting ability scores (before racial adjustments) both having 35,000 XP.
- The half-elf character has a total of 8 feats and 22 hp.
- The lizardfolk character has a total of 5 feats and 34 hp.

- Spellcasting for both characters is exactly the same.
- Combinig all save bonuses nets a total of 13 for the half-elf and 14 for the lizardfolk.
- Skill points would be the same, but for the lizardfolks -2 to Int. For characters of classes with more than 2 skill points per level, the lizardfolk would lack behind even more.
- The lizardfolk has +4 to Balance, Jump, and Swim checks.
- The lizardfolk has a +5 Natural armor bonus.

So to sum it up, the lizarfolk has 12 more hit points, +7 to skills, +1 to saves, and +5 to natural armor.
The half-elf has 3 more feats.

This seems quite balanced to me, though it probably breaks apart with more fancy races.
On the other hand, Aasimar would gain a huge load of abilities in exchange for one single feat.

Please share your thoughts and help me improve on this.

Shameless promotion to my own homebrew that replaces RHD and LA with class equivalent levels:

http://www.giantitp.com/forums/showthread.php?t=142724

With my system, pseudo spellcaster monsters(dragon, ogre mage, mind flayer, ect) who take caster levels can cast at full power while keeping their racial abilities in return for knowing less spells and having less spell slots.

You don't need to take all the class levels. You could for example take 5 levels of ogre mage and then one leve of sorceror or wizard, and you would cast 3rd level spells just fine.