I think your idea should work, especially if you are already familiar with your hardware synths. Any synth capable of creating a multi-timbral patch should be capable.
I just created a two part layered multi patch in SampleTank without much fuss, using a mute guitar sample on the first part, and a sustain guitar on the second part. By editing the "Velocity Lo/Hi" ranges for each part, I was able to create a velocity cross-fade between the two sounds. By setting the mute to trigger only for low velocity, and the sustain to trigger only for higher velocity. You can provide some overlap with the velocity ranges if you desire some more cross-fade between the sounds.
It would probably take some experimentation to get the exact sound you are looking for, but the approach should work.
Good luck!
Of course you could probably do the same thing by editing an SFZ file with velocity layers and using the resulting instrument in an SFZ based synth like Dimension Pro, or the free sforzando. But using what you already know would probably be the fastest solution.
For future reference, here is a quick visual SFZ editor tool and a free SFZ player:
http://mildon.me/sfzdesignerhttps://www.plogue.com/products/sforzando.html