Not if the dock has all the processing units. The Switch would be a "slave" system, only providing input information, and game data. The dock would do everything. The Switch SOC would only be assisting the process - it wouldn't have to compute game related code on top of the dock. The dock would have it's own SOC and would do all game, graphics and AI calculations independently.
That would be classified as another console not a supplementary unit.
Honestly it does't make sense to do that now. Better to build it from ground up to ensure everything works as intended instead of retrofitted. Use it to bridge the gap next gen with PS5/XBOX4