I will be very honest here and say that seat allocation is a load of bull anyway. I have been to games where there were loads of empty seats around me yet some people insisted on sitting in the seats that I had just randomly sat on. If anything certain parts of stadiums should be standing. Gate 4, for example, should be all standing.
The problem is educational. People in Greece are not able to go to a football match with both sets of fans without any trouble. I am not saying to become like the UK or (God forbid) the US (although I was fairly impressed with LAFC's fans), where the atmosphere is quite boring. At least be like Germany where the atmosphere in the stadium is great. Even there fans fight each other but just not in the stadium. If you really need to fight somebody else just because they support another team then find somewhere like a warehouse or the woods, arrange a time, and let all of your psychological issues out.