Can I repurpose a 2TB Time Capsule as an external drive?
Does any way exist to repurpose the device as just an external hard drive?
Yes, if you want it just to be an external drive. Following this iFixit guide to Disassembling a Time Capsule.
You can remove the internal Hard Drive and place it into a dedicated USB external drive enclosure.
As far as I am aware, you cannot disable the core functionality without also disabling access to the drive.