I've been thinking about this a lot lately. To answer CapnZapp's original question unequivocally, no, you can't create a magic item with the traits of multiple items using any rules in the PHB, DMG or AV. (It's possible that such rules might one day appear in Dragon or some supplement, but they aren't there yet. And Artifacts shouldn't count since they use totally different rules and fulfill a different role in the game.)
I like some of the rules suggestions listed here, particularly LightPhoenix's, because of how simple it is. Question though: In your example, a +2 flaming fireburst longbow is level 8. This makes it cheaper than a +2 flaming longbow, which is level 10. Doesn't that seem weird?
The inherent difficulty I have when coming up with a rule for such items is balance. I think the bonus-by-level is very important in 4E and that trading off between bonus and properties is generally a bad idea. (Not every trade-off is a fun trade-off.) However, simply using price is a questionable balance tactic because gold income is not guaranteed. An item with the traits of multiple items is, in many ways, like having extra item slots; buying extra item slots seems sketchy. Trying to balance multi-items against character resources (maybe carrying one reduces your healing surges or number of item daily powers or requires a feat) seems weird to me, too, though.
-- 77IM
I like some of the rules suggestions listed here, particularly LightPhoenix's, because of how simple it is. Question though: In your example, a +2 flaming fireburst longbow is level 8. This makes it cheaper than a +2 flaming longbow, which is level 10. Doesn't that seem weird?
The inherent difficulty I have when coming up with a rule for such items is balance. I think the bonus-by-level is very important in 4E and that trading off between bonus and properties is generally a bad idea. (Not every trade-off is a fun trade-off.) However, simply using price is a questionable balance tactic because gold income is not guaranteed. An item with the traits of multiple items is, in many ways, like having extra item slots; buying extra item slots seems sketchy. Trying to balance multi-items against character resources (maybe carrying one reduces your healing surges or number of item daily powers or requires a feat) seems weird to me, too, though.
-- 77IM