They haven't shown an interest in creating worlds with alternate rulesets at all - probably to keep balance issues simple. I think alternate rulesets could be an interesting way to keep the game fresh and new if it doesn't create too many obstacles.
'No plundering' is hardly the one that's going to draw me in personally though.
Perhaps something that made plundering more important.
Or popular GB restrictions (i.e. No Arc).
Or no diamonds (one can see they'd have a motive NOT to do this one - but it'd make for a good 'fair competition' world - perhaps simply no diamonds for FP, goods, or event currency - so they can still make some income but the benefit is at least limited).
Or even just simple things like 'double all goods costs' to see what an economy with more goods pressure looks like.
But at this point I'm off topic