You can play d5 c6 e6 Nf6 (in almost any move order) against anything. If there's a white pawn on d4 then you'll eventually go for the c5 or e5 break (after finishing or nearly finishing development). If white has played e4 then you'll end up in some french or caro type position.
You said you can play it against anything. Could you reasonably play it against e4 or c4? How would that work?
I heard there was a Meran setup you can play as Black against almost anything. What is it? I have the following written down, which seems to be a mistake.
1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.Nc3 e6 5.e3 a5 6.Qc2 a6
What is the correct line, and what is it playable or not playable against?
My understanding is that this might be slightly different from the Semi-Slav Meran opening.