I don't see the need for an even more powerful Pi Zero. I'd say just have a modernized version of the original $5 single core Pi Zero, or ok the wireless version was good too. Maybe even have a 128MB config (original one was 512MB before the DRAM shortage) to keep the price down. Model A same same, who needs it if it's not a lot cheaper than the B.

I do like the Pico series and it would be cool to have one of those with memory protection.