I had to reread your question a few times 
but I think I understand.
As somewhat referenced in your prior topic - Can mobile app be created for projects developed in local server
You want to know if you can make two different applications (Blynk and whatever) share resources/control over something.
The answer is sure… if you know what you are doing and have relatively similar programmable access to both applications development (AKA your Blynk project & code as well as for whatever).
Lots of others have done the same thing with Blynk and NodeRed, Blynk and Google Home, Blynk and Amazon Echo, Blynk and Virtuino… and so on…
So basically… It all depends on your abilities.