Like I already told you here, there can be many different reasons for this behavior.
Clearly, the boot time is related to the amount of entities, because the more entities Hibernate ORM has to analyze, the more processing needs to happen.
You can customize BytecodeProvider if you want, but I doubt that it has to do with that. The easiest way to figure this out, is to just use build time bytecode enhancement and see if that improves your startup time.