I've yet to find a soft synth that was optimized for live use, which is why I've never been tempted to do so. When I'm on stage, my hands and feet are busy enough without having to reach for a mouse to pull up a patch.
What you really need is a synth that was designed specifically for live use. It would allow you to load up a series of patches and select one with a single keystroke. It would have a performance mode wherein keystrokes are limited to a subset needed for this function. It would not require a separate host, and it would never require looking at the laptop screen after initial setup. It would support patch changes via MIDI keyboard controllers.
If you find such a synth, let me know!
The closest thing I've seen like this have been with samplers: Kontakt and Omnisphere. I've seen the Korg NanoKontrol controller used to quickly toggle between patches, and that's about the slickest solution I've seen so far. Even that's a little constrictive, since you can have a maximum of only 16 patches queued up. But Omnisphere, at least, does have a performance mode intended for live use.