Cook chickpeas directly in soup?
I don't see why not.

I make channa masala from scratch - fry onions, garlic, chilli, add spices, drop soaked chickpeas
...and enough extra water so it will absorb and evaporate in the required time.

That's your only bit of guesswork, but for soup that's probably not as crucial as for a dish which is served almost dry.  

What may be your sticking point -  you may have to salt towards the end, or they will be tough. As I don't pressure-cook, I'm not sure how easy that would be. For regular stove-top, it would be 30 minutes before the end of a 2-hour cook.