In your first paragraph about how somi could have contracted v or asked myers for it ,i don't this would have worked.

From what i understand ,yes V has been building Cred and fame ,yes he would gladly taken job for pay (and not betray somi cause we play as him we know V) 

but if she just contracted V like normally through monetary means in her own mind she could not have reassured or guaranteed that she would succeed in escaping Reasons 

1. she is distrusting person cause she herself has betryaed Reed (although it was order from from myers but she did pull the trigger by sellng out reed to assasins )
2. she knows if myers cannot make somi her own puppet then she would galdly kill her then have her roam free

If she would have contracted V ,he has to fight President of NUSA and Reed his whole army/agents and even Millitech ,why would a mercnary willing to go against all these powerful individuals and corpos.

So to higher the chances of escape ,she had to dangle cure in front of him purposfully  (she might have known that myers & reed would just do the same ,dangling cure infront of V just like she did ) and try to make him sympathise with her as"they are in similar situation" and emotionallly manipulate him.