Your reference thread wasn't about a Freestyle game.
Regardless, back then when I advised not to miss turns intentionally I was looking at it as something that can be too annoying to be accepted in general. I still do and I think many would still agree. I came to the realization that people will always find a way to make back to back turns in Freestyle games. So for this "freestyle issue" - play as you do.
Intentional deadbeating is still mentioned in the rules so don't resort to it. If you are missing turns in order to hold players hostage then that is also against the rules.
For this case, as you say, "intentionally missed his turn in Round 3 (Freestyle game) in order to achieve unfair benefit that he and his two teammates can all start Round 4 turn before my team" - rate them as you deem necessary and/or put them in your Foe list.
Don't blame me - blame the people who resorts into finding a way in order to have that back to back turns.
If you want to make it an official rule, perhaps put up a poll in the Conquer Club Discussion forum and see if the Community wants it make it illegal then we'll see.