...
The key element if IBLT would be a structured ordering of transactions within a block.  My personal feeling is that this is like the difference in handling ability between water in liquid form and water in solid form.  An ice cube is much more flexible to transport, and much easier to match to a mold (e.g., an identifiable ice tray configuration), but it is also more brittle.  An ice cube is also much easier to catch in a strainer than it's liquid counterpart.