9#%002M

You can't please everyone, please delete the tournament thread, I no longer want to run it.

This is the key phrase. Everything that follows would have been better left unsaid.

Or, as an alternative, reset the registration and let only those who are interested register.

As an option, yes. I see two options. First: leave everything as is and reset the registration. Second: run the tournament as usual with pre-made maps without underground, as before, and continue working on the mirror map (up to reducing its size and the number of castles).
Perhaps it would be a good idea to launch a poll? Personally, I accept both options, I will play in any case.