I hear what you are saying, and I guess that there is no harm in experimenting. It is just that, IMHO, I would have preferred having 2 ounces of really good port then an entire bottle of wine that was an attempted fix.
Fran,
The important thing here is to determine what went wrong with the wine in the first place and to take steps / change the procedure that you are using to ensure that it does not happen again.
If the wine is flat and low alcohol, then have you considered upping the brix and, perhaps, extending the maceration prior to ferment?