To be honest I think, we missunderstand the problem.
People don't play playoffs not because of the time. They had time to play 50 games at least (one month season or more) so playing 4 more games is not a big deal for them
. The real problem and the one where TUS can makes the difference is how motivate people to play playoffs. And since the community isn't that old I think it's all about doing a big show off about the winners. For exemple, write it in big at the home page / Make their nickname gold or special / ...
In Fact something to be able to make someone who doens't know about worms thinking about a playoff winner when he sees him in forum "wohoo he must be leet". Same goes with clan.
And in my opinion the best way to handle it is by changing the avatar of someone who post in forum for exemple