Mind Sub-system: Wonders of the World

I'm still alive (despite the lack of posting) -- just been very busy with work and other matters.  I've still been putting some brain bytes towards a good game sub-system for characters based on the mechanical arts or "mind."  I've got an idea I'll post now and another which is percolating and will come in a bit.

Why not use the Wonders of the World?  What better symbol than the ultimate achievement of man's engineering prowess?

• Great Pyramid of Giza 
• Hanging Gardens of Babylon
• Temple of Artemis
• Statue of Zeus
• Mausoleum at Helicarnassus
• Colossus of Rhodes
• Lighthouse of Alexandria

Pros:  There are seven.  This means that one can be allocated for each of the seven classical planets and mechanical arts.

Cons:  There are seven, so this removes the ability to use the Wonders as a theme for a game.  There also aren't any obvious tokens which can be used.  You'd have to use some sort of custom token.  The wonders also have a lot of baggage and/or vague meanings.  Finally, unlike the playing cards in particular, they are hard to combine for additional complexity (suit + numbers).