I am running home assistant through raspberry pi. I have a few zwave devices I would like to connect. I have a nexia bridge instead of a zwave stick. Can I use the bridge or do I need a zwave stick?
To use the builtin support for z-wave your going to need a openzwave supported z-wave usb device.
To use the bridge you have there would need to be support for that bridge in particular.
I’m unfamiliar with the device in question so I don’t know if you can use right now.
here is a link to the manual. It has some info but not sure if that helps understand the product in question.
Basically what I am thinking is that I get the PI to communicate via IP to the bridge since they are on the same network. Then use the bridge to sync all of my zwave devices similar to plugging in a stick.
I do understand what it is that you want.
Problem is that to integrate with HA there needs to be a component that gives support for your device/hub.
As is now there isn’t one. If you can find an api or similar for external devices to interface with your nexia bridge then there might be a future component that will support this device. If there isn’t then the odds are low for that.
Even if there is an api it will be very dependent on a developer having access to the hardware in question.
Next step for you right now if you would want to use the nexia bridge would be to start digging for that information. 
i made a call today. I would basically need the zwave stick to connect to the bridge anyway so I am going to sell the bridge and get the stick. I just didnt want to get rid of the bridge and then find out it was an amazing addition. Now that i know its not im ok to get rid of it.
Sounds like a good plan. Good luck =)