This was inspired by Mark Langsdorf's in-depth rules idea which seems to have springboarded off of my own half-baked musing on campaign direction.
He mentioned a way of curbing the Power enchantment, something I've worked on the extending and limiting abuses of self-powered magic items.
But his post sparked another idea, which is kind of obvious in light of DF's approach. This can potentially work as a replacement for the Charged Magic Items in Pyramid 3/36, as well.
(Editing later: I forgot to mention Power Reserves from DF 8, pg. 47. This is essentially the same idea as Dedicated Reserves except that it fully removes the idea of self-powered items and user FP powering magic items.
What if, for DF, we eliminated the Power enchantment?
You could still use it as a mechanism for determining the cost of an "always on" item that doesn't already have a preset price - GM's discretion.
But in general, it's gone.
Instead, every item is a Power Item. These would not be limited to the usual one-Power-Item-per-caster rules, because it wouldn't be useful for anything but casting the spells of the item itself.
You have to recharge the power normally, in town, basically between adventures.
Magic items being recharged would not be able to maintain spells, eliminating the "cast for free on everyone" hand-around of magic items. You can't cast the spells in town, then get the item re-charged.
Two approaches work for this:
Mundane Value (AKA Normal Power Item Rules)
A magic item can hold power based on the mundane value of the underlying item. If you have an ornate wand studded with gems worth $5,000, it acts as a $5,000 Power Item = 18 Power.
A magic item can hold power based on the magical value of the underlying spells. Straight up $1 = $1 costing makes for very high power levels. Instead, use 1/10th of the magical value (at $25/point this means $2.50/point) to determine the maximum power. Have an item with 2000 power worth of spells? That's $50,000 item, and acts as a $5,000 Power Item = 18 Power.
You can use both - the higher of its magical value or its mundane value's Power Item value. It's probably worth tweaking the value of enchantment to taste.
This approach is basically saying, generically enchanted magic items never depend on user FP to power them. They must always have some kind of internal charge, be it making it a Power Item (in DF) or having a Powerstone (in normal GURPS Magic rules). You could apply the usual rules - Powerstones would be 3x as effective for their size because they'd all need to be Exclusive Powerstones, for example. You just don't allow other options.
You may discover better items that have absolute self-power (a staff that can throw 1-pt/turn fireballs for free, say), but they're the result of lost enchantments, powerful wizards, happy critical successes, etc.