The only way to be able to reproduce exactly the tyros 4 styles on a software arranger, is to use the samples of the Tyros. If a software compagny start selling Yamaha samples, I am sure that there is here some copyright problems.
So I would say you can get a decent and very good sound and CORRECT and acceptable interpretation of the yamaha styles on your hardware or software sound module, but not exactely the same as the original keyboard.
We have an algorythm to render the megavoices on any sound modules. Of course it's not as cool as the Yamaha, but it will be good.
I will post soon some MP3 with tyros 3 styles.
I can't talk on LS v12, because it's not my product, but most of the vArranger buyers have used LS one day
If you are interested to enter into the vArranger world, just let me know.
I think exigent musician like you is a best for us

Dan