You will not be able to inject compiled classes/byte code into your apps remotely. We do not allow you to update the dex files either. In-fact that is banned by Android play store.
The same goes for the Apple app store as well.
However, you can create patches using Hansel dashboard and push them to the apps in production. Hansel converts the patches into a proprietary DSL (domain specific language) which is interpreted dynamically by the Hansel SDK at runtime and executed.