There simply isn't a single stand-alone sampler that has enough real-time and modulation flexibility, so most people use modular patcher programs (Reaktor, Max/MSP etc.) for that kind of stuff and more.
I would recommend either Usine or Bidule, because they are the easiest ones to use and can be used as VSTs , as opposed in addition to being running as stand-alone applications. And they can host 3rd party VSTs in patches, so you can throw in e.g. Alchemy and just attach controls to it + add effects and more:
Another option, although a total overkill for just simple sampling, is Kyma.