I'd like to see objects that can't be carried by just one type of Pikmin so you do get some circumstances where Pink Pikmin and others are carrying items, that'd be cool.
Lets say, for example, there's a stream with an item across the other side. Blue Pikmin can cross over there but can't cross back because the stream is too deep at the side they first entered. The Pink Pikmin alone can't carry the item for whatever reason (you only have a certain number of them lets say), so you send over Blue and Pink Pikmin. Together they carry the item, the Pink Pikmin enabling the Blue Pikmin to walk across the surface of the stream... Jesus style!