If you start a new family, you are no longer a husband to your disabled wife.
We'll leave alone the fact that this situation would mean you are living in sin with a concubine and possibly having illegitimate children.
Another repost because no one will respond:
Suppose I were in a PVS. I've told my wife I want the tube pulled.
Scenario A: She pulls the tube, five years later she meets someone new and starts a new family.
Scenario B: The courts don't let her pull the tube. My body stays alive for decades. Now when she meets someone new five years later it is called adultery. But I don't want my wife to put her life on hold for decades while she fights a legal battle.