Magic Item CreationThis is actually a misapprehension turned around into a functioning mechanic. Back in the old days, though my rulebooks were BECMI D&D, I still picked up a lot of AD&D supplements because I was eager for material and there was so much more of the AD&D stuff available. Mostly I ignored the minor stat differences, but when enigmas like "non-weapon proficiences" and "3/2" attacks with no precedent in BECMI got in the way, I just made a wild guess. This included the XP values listed for magic items, which for some reason I surmised were costs players had to pay for wielding the items ("You're taking the sword +1? Alright Jerry, subtract 400 XP from your sheet") rather than a reward for finding it amongst monetary treasure (I suspect due to my notion that AD&D was "advanced" because it harshly penalized characters for every advantage).
Actually, this makes sense if applied to magic-users creating those magic items. In addition to spending time and gold, they need to give up a portion of their essence to give the item power, represented by the XP cost. I'd just use the XP values from AD&D (yes I did finally get those rulebooks) maybe doubled or tripled. Also, I'd limit PC magic-users to the creation of one durable magic item per class level, to avoid them spamming out bushels of +1 daggers rather than ever leveling up. They can still create as many potions and scrolls as they can afford, with no XP cost.
I'll have more to say about Earthdawn's sharply eccentric advancement system and how it compares to old-school D&D, but for now I'd like to swipe it's XP-for-attribute-raises mechanic. The unchanging nature of attributes in old-school D&D occasionally perturbs me, so it's an easy fix to let players impede their long-term "skill" gains via levels for the short-term benefits of attributes. Eyeballing it, I'd rule that, once every class level, a character can raise an attribute of their choice one point for the cost of 500 xp per point of the new attribute rating; going from Strength 8 to Strength 9 would thus set the character back 4,500 XP. I like that this gives the player a way out of being stuck with a attribute forever on the cusp of a modifier threshold, though I imagine it opens up an exploit if the GM is offering XP bonuses for high attributes (I don't).
And now to prevent this post from just being a wall of text, here's a picture of a stolid ranger by Caitlyn Kurilich, who looks like they've advanced a few levels: