Multiple Weapon and Armor Enchantments in 4e pt. 3

In the pat I have discussed the process of putting multiple weapon and armor enchantments on a single piece of gear. Today, I will get down to the crunch and explain my homebrew rule for making this possible.

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Combining weapon and armor enchantments is very similar to Multi-classing in the most basic 4e form. The first thing you will do is do is determine the base item. In other words, you must first select a piece of magical armor, or a magic weapon, which you want to put an additional enchantment on.

You can put any secondary enchantment onto a piece of gear as long as that enchantment would be legal if it were the first. In other words, you can’t put an enchantment that requires the gear to be cloth armor, when putting it on a piece of plate. This follows the standard rules for enchanting items.

You can only put secondary or tertiary enchantments on weapons of higher level. In other words, the base weapon’s enchantment level must be higher than whatever enchantment you are putting on the weapon or armor.

The cost to put a secondary or tertiary enchantment is reduced by 25%.

Enhancement bonuses from enchantments do not stack, you always use the highest enhancement bonus from either enchantment.

In the case of weapons, always use the enhancement bonus with the highest critical high bonus.

All properties from any enchantments on the weapon or armor always remain active. Regardless of the number of enchantments on a piece of armor or a weapon, the properties on that piece of equipment are always ON.

Weapon powers are limited in the following ways.
At-Will and Encounter: When a piece of armor or a weapon has multiple at-will powers granted by different enchantments, regardless of the type of action, you can only use the at-will power of one weapon per round. In other words, you must designate which weapon you will make at-will and encounter powers with during that round. When you spend an action point, you may use a power from a different enchantment.

Daily: When a piece of armor or a weapon has multiple daily powers granted by different enchantments, regardless of the type of action, you can only use one daily power per encounter.

Multiple Weapon and Armor Enchantments in 4e pt. 2

There are several things that need to be considered when trying to make a homebrew rule like this. I guess because of the nature of what I am doing that things are going to get broken a bit, but unbreaking them is something that will just have to come on a case by case basis.

When it comes to armor and weapons you are looking at several things that need to be balanced. The most important element in my mind has got to be the cost - this will either make items totally unaccessible or game breakingly powerful. GP cost is the great balancing engine of 4e item management (unless we are talking essentials, and I am not).
Level - another very important element to consider for combining any two items or any three for that matter. Putting two properties of vastly different levels together could be very broken if not managed correctly.
Type - For both armor and weapons, if there are type restrictions for an enchantment, it is going to have to carry over to both enchantments.
Enhancement - where do the flat bonuses go?
Properties and Powers - Probably the reason you are going to be taking two or more different enhancements on the same weapon. They are going to need to be balanced in some way.

Well, these are the basic things I am taking into consideration for this homebrew rule of mine. Anybody think I missed something?