considering the above use case you explained, even if the ble module could work flawlessly with blynk, you couldn’t use it without internet, because in the current version the blynk app is designed to use internet for authenticate the hw.
what i’ve done and it could work really good in your case too, is to create a “local” blynk server with wifi. thus you can use blynk + wifi in full potential, no internet needed!
read this:
Setup PI ZERO W as ultra portable server and AP (tutorial)