Can you enchant a plain +1 item to a +1 with property?
The Enchant Magic Item
[ddi] says ... Alternatively, you can use the ritual to upgrade a common, uncommon, or rare item to a more powerful version of the item that is 5 levels higher.
Which I read as e.g. +1 sword to +2 sword, or +1 Flaming Sword to +2 Flaming Sword, but could you do +1 Sword to +1 Flaming Sword ?