A lot of users also record with their Garmin (probably Suunto also) devices because those incorporate the Firstbeat tracking and analytics. While the accuracy of that data is up for debate, it is inevitably considerably worse if it misses indoor training on Zwift.
The suggestion, therefore, would be for Zwift to licence and incorporate a number of the Firstbeat modules so that when the file moves across to platforms which support this (Garmin Connect, for example), the data is calculated and separate tracking on a device is not required.
Depending on which modules were used, this could also inform the Zwift training plans and timescales (see comments on training plan flexibility).