Well, the book has a guideline for the size of focus items (YS281). Putting 5-6 focus item slots on an item results in a focus item the size of a staff or a basketball. Adding more will result in something too large to carry around with you. That would definitely fit little chicago.
You could houserule a flaw system for foci, kind of like "Human form" or "Item of power" for characters. Those things could be "fragile" (as in easy for an enemy to destroy), "unreliable" (roll a fate dice, + it works, 0 it does not work, - it reduces the roll instead of increasing it), "stationary" (as above, too big to carry), and so forth. You will get a refund on your invested focus item slots, though an item costs at least one focus item slot and the bonus total can not exceed your lore.
Example: A blasting rod (+3 fire control) costs 3 focus item slots. An unreliable blasting rod (+3 fire control) would only cost 1 focus item slot, since unreliable is a pretty heavy flaw, in my eyes. An unreliable blasting rod (+2 fire control) would still cost 1 focus item slot.
Now with a lore of 3, that blasting rod would be valid focus item. If you made it an unreliable blasting rod (+4 fire power), it would cost 2 focus item slots, but since the bonus of 4 is higher than the characters lore, he can not make such an item.
If you like the idea, I'll gladly gather up a list of focus item drawbacks.
