Well, at least some automated system is neded to count clan wins/losses, some rules for a winning should be specified and other cost effective things. But the main problem is that you would rarely find more than 2 or 3 people who came on the server in advance to bet for a clan before the clanwar starts (otherwise it does not make sense) and then just watch the games (probably the most interesting part if there are good clans fighting) but more than likely you will be the only person who bet there.