You've heard of the Rod of Lordly Might in the PnP DnD 3.5 DM Guide, right? Acts like a +2 mace, can change into a +1 Flaming Longsword, +4 Battleaxe, or +3 Short/Longspear? Very useful little thing to have around. So what if it were adapted to EB as an item in the Epic Shops?
All you'd have to do is add Unique Powers (Self Only) that transform the rod. It's pretty simple to do...it's possible to do it even with Lilac Soul's Script Generator.
Now comes the problem of which weapon's better. Obviously, the +4 battleaxe is stronger than the +3 spear and the +1 flaming longsword. Hows about adding something like Level Drain/Ability Drain/Poison to the spear and adding additional divine damage/increasing fire damage to the longsword to even it out?
Just my thoughts.