I know that would, should and could are the past as well as the subjunctive forms of will, shall and can, respectively. At least that's how they started out; they have taken on lives of their own since some probably Anglo-Saxon or maybe Old English or Middle English beginning.

I am sorry to see the subjunctive vanishing, myself. I know that everyone now says "I wish I was in Dixie" but I miss "were". When I taught Latin and we got to the subjunctive I told students I was going to do a grammatical magic trick. I would write on the board "I were in New York" and I'd ask them if that sentence was OK. They'd all say no. Then I told them I was going to MAKE it OK without changing any word on the board. Then I'd add "If only--" or "I wish--". That would introduce them to the difference between subjunctive and indicative. I also used to draw someone watching TV, and I told them that indicative reality was the living room and subjunctive was TV-land -- hopes, wishes, unreality and possibilities. Enough! BASTA!