Yes it does seem like bitcoin is lacking in a few places. You could (try to) add things like

* disconnected operation (solve the double spend problem in a disconnected setting) (this would really make something gold-equivalent)

* a provably correct, but cryptographically secure ledger (meaning real anonymity)

* proof of work based on a single crypto standard seems risky. Use 5 of them.

* provably no way to compromise the network even with overwhelming computational power

Zerocoin is trying to solve the second problem.

Combining 5 proof of work standards just gives you 1 new one. (There might be some robustness to be gained, though.)

Cool, I didn't know about zerocoin. There goes my afternoon.