My guess is that this will be difficult for a number of reasons. One is finding enough free space on the Tracker to store the coprocessor firmware image.
While the Tracker is also an nRF52, and the nRF52 SDK is mostly available to user firmware, none of the additional features like BLE DFU are present. It may be possible to add those in manually.
However, the other problem you will run into is that the Tracker also uses BLE for its Particle Device OS BLE features. It’s highly likely that you will run into issues where the two features conflict with each other. You might be able to turn the Device OS features off, which may help.
I also think you’ll run into a problem with handling BLE interrupts from user code.
A less fragile but more difficult solution would be to reimplement the nRF BLE DFU protocol on top of the Particle BLE API. This is safe and would almost certainly work, but would require some effort because you’d have the reimplement the whole thing because the nRF SDK BLE and Particle Device OS BLE APIs are not at all the same.