If I understand correctly, one of the limitations of doing application level failure injection with Gremlin is that you need to integrate it into your code: https://www.gremlin.com/docs/application-layer/installation/

It might be interesting to combine these approaches and use a traffic split to send a percentage of traffic to Gremlin instead of integrating into the code directly.

Shh, you're going to wake up the TinkerPop Gremlin guy.