After 1. d4 d5 2. c4 c6 3. Nf3, Black usually plays Nf6 or e6 (which blocks his light-square bishop) and I wonder if it is possible for him to adopt the ideas from the London System and play Bf5 before e6. This is a rare move but I wonder if it is sound. After all, black is one tempo down compared with the London System by white. But is black's position solid enough to compensate this?
That is the Slav, but the problem for black in many of these lines, and specifically immediately, is that if 3...Bf5, then 4.cd cd 5.Qb3 forces you to sacrifice d5 or b7 since 5...b6 just loses.
[FEN ""] 1.d4 d5 2.c4 c6 3.Nf3 Bf5 4.cxd5 cxd5 5.Qb3! b6? 6.e4! (6.Nc3) Bxe4 (6...dxe4 7.Ne5+-) 7.Ne5 a6 8.Ba6! Ra6 9.Qb5 Nd7 10.Nd7! Qd7 (10...Ra5?? 11.Nf6++#) 11.Qxa6+-
This is just one example, and white can also play it more quietly with 6.Nc3 instead of 6.e4, but no matter how you do it, it is either the loss of a pawn with insufficient compensation, or worse, death on the light squares.
Lastly, you can try to postpone Bf5, but the same basic ideas are still strong later, or you lose a tempo with a6 putting you two tempi down on the same white opening. Basically, the answer is "no", the position cannot withstand the attempt to bring the B out early there.
P.S. I just looked at your picture again, and noticed the computer eval listed, and that +.73 is modest. It will probably grow after just a few moves.
I tried this about 15 years ago and after 4. cd cd 5. Qb3 I was soon in a world of pain. I've never tried it since.
[fen ""] 1. d4 d5 2. c4 c6 3. Nf3 Bf5 4. cxd5 cxd5 5. Qb3
There is no good way to defend the b pawn and white's minor pieces flow effortlessly into the attack. Nc3, Bf4, maybe Ne5 at some stage, either e3 or even e4, followed by Bb5. Nb5 then c7 may also be on the cards. White can just generate too many threats far too quickly.
I don't remember how the game went after Qb3. Mercifully the healthy mind suppresses deeply painful experiences. Just like touching a hot stove I know not to do it again.
The London Defensive System is actually a named line in the Réti Opening. And yes, it is very playable. You don't see this very often nowadays, because White will try to stop Black from playing it.
Here is a famous game Réti - Lasker, 1924, in which Lasker went for this line and won convincingly.
Look at the position after
From my analysis:
Note how both sides have developed their minor pieces: The bishops are free to move, not blocked by pawns. The knights protect each other and control important central squares.
Black has made good use of the extra tempo White needed for the double fianchetto and completed their development first.
However, White can trade off a knight for Black's (bad) light-squared bishop whenever they want. This means Black has to come up with an active move right now.
Important motifs here are the e2-e4 break by White (which Réti didn't play, unfortunately), and a queenside break per
b5 by Black if possible. In this game Lasker played the aggressive (and not very accurate e6-e5). A rare move that can be punished with e2-e4 immediately. The point is that Black has to take with
dxe4, and after
Nxe4 Nxe4 dxe4 Black's bishop on
d6 is hanging and has to move – losing another tempo. So don't fall for that. :)
[Event "New York"] [Site "it New York USA"] [Round "16"] [Date "1924.??.??"] [White "Reti, Richard"] [Black "Lasker, Emanuel"] [WhiteElo "2550"] [BlackElo "2720"] [Result "0-1"] [FEN ""] 1.Nf3 d5 2.c4 c6 3.b3 Bf5 4.g3 Nf6 5.Bg2 Nbd7 6.Bb2 e6 7.O-O Bd6 8.d3 O-O 9.Nbd2 e5 10.cxd5 cxd5 11.Rc1 Qe7 12.Rc2 a5 13.a4 h6 14.Qa1 Rfe8 15.Rfc1 Bh7 16.Nf1 Nc5 17.Rxc5 Bxc5 18.Nxe5 Rac8 19.Ne3 Qe6 20.h3 Bd6 21.Rxc8 Rxc8 22.Nf3 Be7 23.Nd4 Qd7 24.Kh2 h5 25.Qh1 h4 26.Nxd5 hxg3+ 27.fxg3 Nxd5 28.Bxd5 Bf6 29.Bxb7 Rc5 30.Ba6 Bg6 31.Qb7 Qd8 32.b4 Rc7 33.Qb6 Rd7 34.Qxd8+ Rxd8 35.e3 axb4 36.Kg2 Bxd4 37.exd4 Bf5 38.Bb7 Be6 39.Kf3 Bb3 40.Bc6 Rd6 41.Bb5 Rf6+ 42.Ke3 Re6+ 43.Kf4 Re2 44.Bc1 Rc2 45.Be3 Bd5 0-1
In its ideal form, you play 2...Bf5 before committing your c-pawn, keeping ...Nc6 as an option, and possibly defending Pd5 with ...e6
Of course, if White has already threatened your d5 pawn with 1.d4 d5 2.c4, you have to consider, after 2...Bf5, the immediate capture 3.cd5, when Black continues with the shocking 3...Bb1 and the play becomes lively, but quite different from your usual London system !
In case there is no pressure against d5 and you have time for both 2...Bf5 and 3...e6, Black is more solid. A quarter of a century ago was played the famous gem Kramnik-Shirov, Linares 1994.