I've found it's best to just rebind the x55 along side of the VA commands. Otherwise you've got to not only change them in game but also in VA itself.
In the in game controls menu, there are two columns. Once you move the HCS binds files and select the layout from the in game drop down menu, Venus will have all her commands in the left column. You'll just have to rebind your HOTAS to the right column manually.
I just use the windows default speech recognition software. There'll be a little tooltip when you start VA that'll tell you where to go to set up the software. When it comes to modifying the commands in VA, I should've mentioned I meant the spoken commands so you can have some variance in what you need to say, otherwise you have to be very specific to initiate a command.
I find VA is great for immersion, and like you said, you might need to add (personalise it) with your own take on commands.
It is quite easy to change though.
If you find some commands like "deploy weapons" not to your taste, you can add "guns" or "bring the pain" to the "say command" by using ; in between the words you add and the existing ones.
Also the newer version of VA lets you add a lot of extra random sounds to each command, so you get different replies to each command, you can even easily add a whole folder full if you want.
I have Dark and Astra, i also use power grid on a tablet, again loads of extra labelled buttons, having both these enables me to look for a cheaper Hotas, as i don't really need all the buttons of the more expensive ones.
but i don't like relying on VA, (hence power grid) it can sometimes be a bit unreliable, and you do need to do the voice training a few times.