heh how are you going to get the soulstone, unless you already have an army that can take it...
however, i would need more reports to think things have really been changed. Once, in a DomII game w/ norfleet's ermor neighbouring, a nice independent provice bordering my start had lamias and a lamia queen.
the lamia queen had the soulstone.
it stayed indepent for a long long time. though i did try assassinating her (f9s9 marignon bless) for funsies