1...d5

Interestingly enough, you've captured my repertoire as Black for the past 4 years. :)
You're right ... 1.c4 d5 will get you a sound thrashing at the hands of a strong player in an actual OTB game, but at blitz controls, pre-moving 1...d5 can't be a total crime.
You're also right about the Bb5+ Scandinavian line. This is precisely why I quit playing it in tournaments last year.
Though in the interests of getting better, you're better off learning better "one size almost fits all" systems like the Dutch/KID/QGD transpositions than 1...d5.
If you're playing "up" most of the time, the stronger players are guaranteed to cash in on sub-par opening choices.

I have never been a fan of the 2...Nf6 Scandinavian for black, but it is fully playable and may take white out of his comfort zone early on in the game. Against 1.c4 I recommend you look into 1...c6 or 1...e6 hoping to transpose into a QGD or Slav, depending on which one you choose. You will have to learn some alternative plans for when white refrains from playing 2.d4, but I think your position should be fairly solid. 1.c4 d5?! is just better for white, he trades a flank pawn for a center pawn and gains time on the queen if 2...Qxd5.
1. ...e6 might not positionally work well against 1. b3 or 1. e4, but for practical purposes, 1. ...e6 does work against everything as well
I don't understand the motivation behind this idea. It's not like it's hard to remember your first move against a half dozen white opening moves. I could see if the defenses were thematically similar, but the structures and dynamics are completely different between say, the closed games of 1.d4 d5 and the Scandinavian.
If you're trying to make it easier to keep yourself on the straight and narrow through the opening waters, you're further ahead with something like the French/QGD combo, which bases upon similar ideas like a common e6/d5, a troublesome bishop to overcome strategically, and a thematic c5 freeing manouver. Or a French/KID that bases play upon static central pawn chains. Or a Dutch/Sicilian that bases upon seizing opposite-side space, and active counter-attacking chances. Or even a modern against everything.
These one-first-move-against-anything repertoires end up being more complex and less effective, unless you're into memorizing reems of theory, since you have to understand a half dozen different strategical themes, rather than one or two.

scratch that, d6 may not work good against 1. b3 and e6 may not work well against 1. e4
I disagree. 1.b3 d6 fights for control of the dark squares and 1.e4 e6 is a standard French Defense.

I don't understand the motivation behind this idea. It's not like it's hard to remember your first move against a half dozen white opening moves. I could see if the defenses were thematically similar, but the structures and dynamics are completely different between say, the closed games of 1.d4 d5 and the Scandinavian.
If you're trying to make it easier to keep yourself on the straight and narrow through the opening waters, you're further ahead with something like the French/QGD combo, which bases upon similar ideas like a common e6/d5, a troublesome bishop to overcome strategically, and a thematic c5 freeing manouver. Or a French/KID that bases play upon static central pawn chains. Or a Dutch/Sicilian that bases upon seizing opposite-side space, and active counter-attacking chances. Or even a modern against everything.
These one-first-move-against-anything repertoires end up being more complex and less effective, unless you're into memorizing reems of theory, since you have to understand a half dozen different strategical themes, rather than one or two.
Haha he's right 1.e4 d5 is nothing like 1.d4 d5 and 1.c4 d5 is just bad.
Even though without realizing it, I lumped g6 against everything into the same boat. Which is awful advice for someone seeking to simplify things, since you'll find yourself dealing with Pircs, KIDs, and offbeat crap that actually gives white an advantage anyway since your position starts off so passively. Even that God-forsaken Bc4/Qf3 Scholar's mate/Monkey's Bum stuff keeps black on his toes against the modern. So mentally scratch that bit about the modern from my "easy repertoire" advice, if you would. Total brain fart.
I don't understand the motivation behind this idea. It's not like it's hard to remember your first move against a half dozen white opening moves. I could see if the defenses were thematically similar, but the structures and dynamics are completely different between say, the closed games of 1.d4 d5 and the Scandinavian.
If you're trying to make it easier to keep yourself on the straight and narrow through the opening waters, you're further ahead with something like the French/QGD combo, which bases upon similar ideas like a common e6/d5, a troublesome bishop to overcome strategically, and a thematic c5 freeing manouver. Or a French/KID that bases play upon static central pawn chains. Or a Dutch/Sicilian that bases upon seizing opposite-side space, and active counter-attacking chances. Or even a modern against everything.
These one-first-move-against-anything repertoires end up being more complex and less effective, unless you're into memorizing reems of theory, since you have to understand a half dozen different strategical themes, rather than one or two.
You do make a strong case... however, I have tried both the French and the Sicilian, and it seems I just cant memorize the theory... Unless you can give me some non-theoretical lines that still use common French/Sicilian ideas?

Silman has a rather nice "one size fits all" repertoire for players starting out which covers a "response to everything but 1.e4" using QGD + transpositional ideas.
http://www.jeremysilman.com/chess_instrctn_bgnrs/120603_crt_easy_op_rep_bk.html