I've had some of your soup too, and it was very nice:)
However, personally I generally don't like putting chemicals and/or artificial ingredients into my food. Soy, though, is great for seasoning, and I've done that myself - and of course experimenting is great. I just prefer experimenting with natural (mostly fresh) ingredients.
Btw, if want to add some seasoning to soup (or other dishes) next time, in a not entirely natural way, rather than using Bisto, try some of this stuff:
https://www.tesco.com/groceries/en-G...ucts/257442342
Trust me, it's far better than Bisto!;)
Marco.