Rare Variation in Queen's Gambit

Hello all,

I have a question about the following variation:

Is there something that is positionally/strategically wrong with Black's idea to just grab the c4 pawn? It looks like 5. e3 and 5. e4 would be the main replies.  I suspect something must be wrong with Black's play since it is a rather rare variation, but I am not sure what it is. Any comments would be appreciated. 

I would like to add that 5...c5 seems possible after both 5. e3 and 5. e4, which means that White is not able to completely dominate the centre.

Back gives up a center pawn for a flank pawn, and cannot hold onto the pawn.

I do see that, but surely if the Queen's Gambit Accepted is playable and considered "solid", surely this sort of setup should not be that bad either. It may be the case though that White has a better version of the QGA since the bishop has found its way to g5.

It looks fine

5. e4 is probably more challenging to play for black than 5. e3 as after 5. c5 6. Bxc4 black can play against an Isolated pawn with cxd4 7. exd4. If 6. nf3, still cxd4 and after 7. nxd4 be7 white gets a bit more piece activity but the structure is symmetrical and black isn't far behind

So after 5. e4 c5 white has a few options on how to continue

if 6. nf3 then cxd4 7. nxd4 and after bc5 the position looks quite nice for black as the knight has to go back to f3 which seems odd

if 6. dxc5 it leads to a balanced endgame in which after qxd1+ 7. rxd1 Bxc5 8. e5 nfd7 9. Bxc4 nc6 black has a lot of pressure on the e5 pawn. An example continuation: 10. nf3 0-0 11. Bf4 h6 12. 0-0 g5 13. Bg3 g4 14. nd2 and black picks up the pawn

So I suppose the only other challenging response to 5. c5 is to play 6. d5 which looks ok after be7 7. Bxc4 exd5 8. exd5 black gets the Isolated Pawn again but the pawn is a bit more advanced than in the other variations and the f6 knight pressuring the pawn can be eliminated with Bxf6 in the future

Still, looks good

The diagram comes out with white in a slight upper hand because of the pressure of f7. So black's f6 bishop is basically pinned because if it moves there can be an easy checkmate.

I don't see how tbh. if 11. nd7 12. d6 nb6 black removes any possibility of a battery aiming on f7

unless you're saying that the f1 rook would be putting the pressure on f7? which isn't really possible as the f file can't be opened up by white feasibly

After Nf3 your right back in a Vienna, so I would agree with @DasBurner that e4 is something that needs to be looked over. I can't see how black isn't fine though.  This structure is pretty common in the Vienna/Ragozin/QGA so a lot of lines would most likely transpose.

I think the following lines are a fun alternatives to the c5 lines that you guys were looking at: