I don't really know anything about unity so I can't help you with that specific.
But in general drivers can be anything. What I said before was a specific usage of it, and what you were talking about. Drivers are nothing more then a way to automate multiple actions at once. It's most common use is to apply a morph when a bone move automatically, but you can do anything with it really.
Unity has most likely something with the same functionality as drivers. I would be surprised if it doesn't since its a very basic feature.
The issue is prob more on the DAZ side of things. DAZ does a lot in weird ways which make it hard to switch DAZ assets to other software. I don't know if this is on purpose or just by a different design approach. If you would ask me I would say they do it on purpose since they go against the universal standard with so many of their features, it just comes across as delibera.
For example what your describing is in most other 3D software programs done the otherway around. Moving bones apply the respective morphs, since bones are easier to control. DAZ does it the other way around for some reason
Anyway everything a driver does need to be there though. A driver itself is just a switch. It turns thing on or off (or half on, etc.). What it turns on/off needs to be made otherwise drivers don't know what they are doing.
If unity supports some form off of drivers and you can't seem to import the DAZ ones, you should be apply to find the individual parts of a driver and link them again.