Crossfading samples in live performance

Hi,

I'm familiar with and have created an EXS24 instrument that uses the mod wheel to do a cross fade between groups. I'm wondering if there is a way to create an instrument that has a sort of auto crossfade sort of effect. Much like when DJs cross fade between tracks. However, I'm wanting to set up an instrument—if it's even possible—that does the same sort of thing between groups in an EXS24 instrument. I've done some digging and can't find anything of that nature.

The goal is ultimately for live performance. I'm wanting to be able to trigger a long droning sample that goes for about a minute, then push the mod wheel up up and trigger a sample in an other group. The two would essentially crossfade and from that point on, I'm not concerned about sample lengths or groups. Perhaps I'm just not thinking about it in the right way. My plan was to create the EXS24 (or whatever ends up being the best option) in Logic then using it in MainStage. The issue is there's no guarantee how long the drone needs to be. Could be 45 seconds and could be 2 minutes, so I'm wanting to figure out a way that allows me to have a 3 minute sample that can play until it needs to fade out. Note that the sample is not one that could loop, as it is ambient street background sounds.

Any help or guidance would be greatly appreciated.