I think the real difficulty is finding a dance partner. If you take Ray Allen out and assume KG gets better you are looking at the following team:
Perk
KG / Scal
Pierce / Walker
Tony Allen / Giddens
Rondo / House / Pruitt
The biggest need would be a backup Center especially considering Perk and KG both have injury question marks. The next need depends on how much you trust Walker, Allen, Giddens, and Pruitt to contribute. If the answer is not at all, clearly a wing is needed. The talent at the big and wing might not be as good as Ray, but they both need to be excellent players to make up for losing Ray. And I think the C's can get decent big talent without trading, Davis and Powe have both shown to be good players, and Sheed is an option from Detroit.
For the wing spot Shane Battier would basically be the ideal candidate, but there is more or less 0% chance of getting him, so we'll have to see if a glue guy can be found or not. Anyways I don't see it happening in a trade, unless some bad team gives up a high ceiling talent and some draft picks with a high projected value.
Also Artest is not that good IMO.