Thanks for the suggestion, but no thanks. I see no reason to up the tax, I don't think it will create more woe guild, if someone is dedicated they will simply work for it as others have done before them, and an extra 20% or 25% tax will not suddenly make people "zomg I totally gotta woe now/make a woe guild".
However, I do have something else in mind that can sorta come close to this, it's a hat that has a level requirement of 99 and gives more exp from any monsters, thus more tax (no reason to wear it unless you're taxed). This thread made me think of this hat idea, but previously a while ago I had the idea to make a Guild Quest, and this hat would now be one of the product resulting from the quest, along with some recruiting guildmember hats which was the original intended product for it.