Hello Pete!
I don't know Overture, but if you can assign the different voices to different MIDI channels, it should pe possible to work the way you are used to. Nevertheless I want to mention that you might want to use more than four articualtions for an instrument. I guess you would have to add a second staff for such an instrument. Otherwise you will have to take care of keyswitches or MIDI CC data in order to change between articulations.
Best regards,
Andi
Vienna Symphonic Library