Ideas for a new Bitcoin testnet:
Cool, cyberpunk branding and design, so people pay attention to it and want to use it. I suggest "The Bitcoin Chaos Network" or "Bitcoin Chaos", for short. Black and white branding with no Bitcoin orange in sight.
Trading coins for money is encouraged.
Proof-of-work mining identical to mainnet. No testnet fast difficulty adjustment.
Development policy of including anything that has a reasonable chance of being merged into core.
One of Bitcoin's core features is that coins have real-world value. A testnet with coins that have no value doesn't reproduce dynamics essential to Bitcoin, and doesn't encourage real-world use.