My vote is for:
Shrink item : vague, house rule
During size changes, what happens when the spell is obstructed in some way (ie - if someone shrink-item's my armour, what happens? Do I get crushed to death, or does the armour break, or does nothing happen? The same goes for when a shrunk item expands in a space too small for it).
What are the properties of a shrunken item? Does a shrunken item in non-felt form still get frozen in time? Can a shrunken item be damaged in it's shrunken form?
What happens when an item regains it's form while in mid-flight? Can I shrink a huge slab of iron and then fling it at someone, calling the command word mid-flight?
What constitutes an item? The example is a campfire - surely that's a group of loose logs? If I shrink a treasure chest, can I later open it up and take out each shrunk item from within it?
House rules: Shrinking items which are prevented from shrinking, or growing items which are prevented from expanding will cease expanding or shrinking.
A shrunken item is in stasis. Any attempt to destroy, dismantle or otherwise alter the shrunken item (ripping a felt representation, opening a treasure chest, animating a shrunken skeleton, enchanting a shrunken sword) restores it to normal size without any other immediate effect (so throwing a shrunken glass item at the floor simply restores it to normal, it doesn't smash it).
Shrunken items can only be restored to normal size while resting on a surface capable of supporting their full-size weight.
The spell will shrink an item, or a group of items up to the limits set out in the spell. Thus an entire campfire, or a pile of gold may be shrunk.
These changes to the spell allow the spell to be used for it's originally intended purpose (that of easily transporting non-magical goods) while disallowing many abusive tactics (specifically that of using an extremely large weapon shrunken to normal size, then expanding it to cause massive damage).