When I tried to create signet or testnet for CPUchain, I noticed one important problem: mining is difficult. The goal is to create a chain where everyone can get some test coins without anyone's permission. On the other hand, mining should not be too easy, because then the network would be much less secure. The solution I found is test sidechain. To create testnet block, you have to vote for or against taproot in your own block, in a BIP-9 or similar way (to be decided, but BIP-9 is now used on Bitcoin). But then, another problem comes in: that chain would have unlimited coin supply! To fix that, coins should be destroyed when they are moved on the mainchain. In this way, any miner can easily create some testnet coins while mining mainnet coins, just by voting for or against taproot in the block. On the other hand, testnet coins could be later deleted simply by moving coins in the mainnet. All testnet transactions would have Schnorr signatures and tapscript, so that publishing them on the mainnet would be impossible, unless such features would be activated, but even then having some coins for testing would be useful. And still, as long as non-taproot coins would be spent on testnet in a taproot-compatible way, both transaction chains should be safely separated. Also, as we talk about testnet, it is possible to introduce users to such network, simply by letting them spend their coins in more than one way. For example: if someone has some coins locked with some public key (hash), all that is needed is creating spending transaction with Schnorr signature. That transaction would be rejected on mainnet, but accepted on testnet sidechain. And later, any user can simply move mainchain coins and destroy all connected test coins in this way. But, as getting miners support is more important, I think we should stick with block signalling first, because Miner Activated Soft Fork would be safer than User Activated Soft Fork.