To the best of my knowledge, no one is doing Zwave plus OTA firmware updates well except homeseer. They have a utility Included free with their pro line of controllers which can do z wave plus OTA firmware updates, it allows you to update files that you get from other manufacturers to do their updates.
You can also get it as a standalone utility which can run on a laptop with a USB zwave plus stick. You should be able to add that as a secondary to your SmartThings network.
Compatible with a variety or systems including HomeSeer, SmartThings, Wink and many others.
The One that works with SmartThings is a laptop utility. You will also need a USB zwave stick for the same laptop, but you can add that as a secondary controller to your SmartThings Z wave network and then update the software that way. But you will need to get the files to use from the device manufacturer, and they are not all releasing them.
Vesternet did a good roundup article at the beginning of the year about how various controllers/device manufacturers are handling zwave plus OTA updates. It’s not a pretty picture. 