Although never having written bots for planetarion, I have written automation programs for other online games. Mainly for educational purposes or for profit
(I see no actual point in cheating a game, go ahead call me a hypocrite for making them).
One thing it has taught me is CAPTCHA is generally more harmful to legitmate users than it is to the people who bot, because they simply move onto new games are find ways around them. In the case of an online game which threw random CAPTCHA words at you every 5-10 refreshes we found the best course of action was to have the bots upload the image to our server then link to it in an IRC chat room offering incentives to those who helped complete them.
I'm not going to go into specific details, since I don't want to give anyone too many ideas. However the point is simple, any antimacro system is bypassable. The main thing is finding a point where the system is causing least possible harm to legitimate players and maximum harm to bots. In PA's case there are, afaik no bots. However none of the players like the CAPTCHA codes either, so I'd certainly say it would be ideal to change to either simpler maths or a simpler alternative.
.... That was a long winded post to say something rather simple, so anyone who can't be arsed to read it basically:
In the interest of the players make it easier.