...or you could just ignore the 'rule' that says that natural enhancements don't stack with magical enhancements.
I say that if enchanting a simple iron weapon with a +1 bonus makes it +1, why shouldn't enchanting a weapon made of a superior metal (i.e. adamantine) with a +1 bonus cause that to improve it's natural goodness?
Enchanting a sword, for example, to be +1 hones the existing edge and improves the existing balance of the blade to make it that much more effective. So why shouldn't a +1 adamandine longsword be in effect +3 for purposes of attack and damage bonuses but still +1 for purposes of piercing Damage Reduction?
My basic point is that when you enchant something, you make it better at what it does. So why should enchanting an already impressive weapon not improve that weapon's qualities?
That point aside, I want to be clear of something. Say you take a longsword and enchant it with Flaming Burst. Since flaming burst is equal to a +3 enhancement it costs the same amount as a +3 longsword would.
But are do all Flaming Burst automatically gain +3 to attack and damage as well? I've seen DMs run it as such, and it really overpowers things. In fact, it really doesn't work like that, according to the rules themselves. In the DMG, you see:
The Sword of Kas, which is +6 unholy keen vorpal. So considering that unholy is a +2 bonus, Keen a +1 bonus, and vorpal a +5 bonus, the sword should be instead +8. So...IT DON'T WORK LIKE THAT!! HA!
Weapon + bonuses are not automatically granted by slapping on enchantments like Flaming, Returning, Wounding, etc. HAHA!