DISCUSSIONS on “Rules for online games in HoMM3 and formulas for calculating player rating.”

But those who agree to it are already playing without spending 10 minutes deciding whether to cast mass skin or skip their turn.

In my opinion, if you create a decent chess timer for each turn in battle (e.g., 5+2) and include it in the tournament regulations, it would be perfectly fine – if an opponent refuses, you point to the regulations, and that's it.
The main thing is not to start this timer when the opponent has stepped away, and you unexpectedly attack them in the middle of their turn. It makes sense to create an acceptance window (something like accepting a turn during a normal turn transfer).