I think this is a really really great idea. Early game its all about grabbing your stuff and running out on the field to set up or cap that first flag. Well this way it'd be a good bit easier to grab that cheap common item and go. Then while you are out on the field and have some downtime, which happens plenty, you could look through your upgrade paths so that the next time you returned to base to upgrade you'd know what to get really fast.
This would also allow for many more items to be created and/or modded in.
I think artifacts could still be upgradable but they start out differently. They still start expensive but not as expensive as they are now. But they would give you the special ability first and then upgrade with some of the mundane stats. Example, Cloak of Invisibility...allows you to cloak for 5 seconds...further upgrades might give slight mana boosts and perhaps dodge %.
I contrast to normal items which start off with the basic +armor and +HP style of upgrades and then end in the final upgrade giving it either a powerful stat or new ability.
I hope someone with some sort of power reads this topic.