yeah but with that spell, you're asking a mage to have 12 intelligence and making him spend 240 zeon(about) because a +10 weapon has +100 presence. so depending on the base weapon, say it has 20, well you need to cast for a presence of 120. thus the 12 intelligence and 240 zeon.
240 Zeon isn't that much. Plus it has no maintenance so it only needs to be cast but once and you have the items permanently.
EDIT: although 12 INT may take till level 4-6.
I created HOUSERULES for re-forging things (for those who don't have access to Creation Magi),
HOUSERULE: It takes a forge check of on less difficulty than what would have originally been needed to make the items, below that fails to remake the weapon. If the item has a quality bonus and you succeed by two degrees you make it better than before, by +5 (assuming the material can handle it). If you fail by 3 or more difficulties you destroy important materials and decrease the items quality by 5.