Water gas is, conventionally, a mixture of carbon monoxide and
hydrogen which is obtained by passing water vapor over hot coal.
I don't think that introducing your new meaning will simplify
anything!
A gas is incapable of condensing; that is why one distinguishes
a vapor from a gas. Often the region of a simple phase diagram
for temperatures greater than the critical temperature is called
the "gas phase", but the boundary between this and the vapor
phase below that temperature is evidently artificial. I don't
know who thought up this particular convention, but it lacks
physical meaning in my view, and I prefer the old fashioned way.
When one speaks of a gas it should be in reference to a
substance in vapor phase and far from saturation. In my opinion
distinguishing a gas from a vapor by its temperature will surely
lead to misconceptions.