MultibandFx with 2-3 slots where you can load other fx per frequency range.
Yeah we discussed something like that already during developement.. till yet wasn't time for such thing, but definitely it's somewhere on the list..
For now i'm using for this NS2 audio routing capabilities - i simple add sends to let's say 3 other tracks, pre fader (and i put fader of main track down to zero) .. then i filters / EQs on those 3 track to filter out just particular spectrum and put effects on that track to apply just on that spectrum..
Another option is FAC Bandit - very cool multiband (3 bands) multieffect AU unit, currently it has some ovedrives/distortions/lofi and delay modules available for every band, but dev have plans to add more FX types ..
I do as dendy suggests. Works pretty well for my purposes. It would be sweet to have a native three band filter plugin expressly for this purpose that was aware of its two partner instances so that you could adjust the bands on one instance and the other two would auto-update.