There is no reason for a disc commuter bike to be ultra-heavy duty fat tyre tourer. There are plenty are light, agile aluminium CX style commuter/doitall bikes, with discs, rack, fender mounts and clearance for max 35/38mm rubber.

Thru axles provide structural support for suspension forks in heavy use. On a fixed fork commuter, you really don't need them. Is there a mature standard for axle diameter yet?