I wonder if some people are trying to test developers' patience, and force them to start testnet4. But if they do, then maybe this time it should be automatically resetted, for example every two weeks, to kill those speculations about the price of tBTC in BTC once and for all.
Signet already exist though, which is centralized to make it more reliable compared with testnet3.
Multisig with distinct HW vendors is something I'm thinking of. Does signet allow testing of this kind of research?
How about for mobile+LN wallets?
I do think that many wallets don't support signet, while supporting testnet3. However, you can easily test your hardware wallet multisig setup with the 0.01tBTC that faucets give you for free. No need to own 7-10tBTC.