OP's argument is a little bit unorthodox. Generally maintaining homeostasis is seen as a threshold for life and that's why viruses are often excluded, they cannot really maintain internal state.
There's no clearly agreed definition of 'life', and in my opinion, scientists are moving gradually towards an idea that viruses should count as life. Hank Green recently posted that he finds it obvious that viruses are alive.
The argument that viruses are not life has become a bit circular - viruses are not life, therefore, we have to come up with awkward definitions of life that exclude viruses.
You've posited a different definition, which I'd suggest is very close to mine - 'maintaining homeostasis' is meant to express the idea that a cell is able to produce its own proteins in order to control its own environment to its own benefit.
[When a virus changes that environment to suit its own needs, we don't want viruses to be considered life, so we don't call that 'homeostasis' any more - at least, we don't when we're talking about the context of what 'life' is. There are plenty of academic papers that do call this homeostasis, considering homeostasis as an interplay between cells and its viral infections.]
