I would like to see Dawson play in place of Gallas that would definitely strengthen the defence, what about this for a line-up: Lloris , Walker-Dawson-Caulker-Vertongen, Lennon-Sandro-Dembele-Carroll-Bale, Defoe . Whilst I am not in favour of playing this formation at home (4-5-1) with Ade out, this would allow Lennon/Dembele/Bale to support Defoe up front. AVB has to make a decision regarding the Keeper, he cannot keep alternating between the 2,(England tried it years ago with Shilton and Clemence, and it didn't work) and live with it even if it means losing one of them. I don't think Carroll deserves to be dropped and Dempsey does not work hard enough nor is he good enough. Thoughts please.
Ok here goes...
If we are going to play 4-5-1 or 4-2-3-1, then I see no problem with your line up. I agree with Carroll for Demsey and making Lloris the out and out number 1.
I guess the issue is not the formation. As playing this formation or 4-4-2 could equally work well. The real issues are to play a formation which suits the players you have coupled with the style and tactics that creates chances and is defensively solid.
4-2-3-1 gives protection for the back, whilst having a penetrating 3 pronged attack with Dembele linking the play from defence to attack. The play can move through the middle or down either flank but with Defoe up front the ball will mainly have to be played to feet. Bale and Lennon would cut inside to attack directly or pick Defoe or the late arriving Dembele to direct these passes at goal. We lose the option for crosses and headers and Bale and Lennon would not play to the byline and whip crosses in. To play with a small guy up top you need to play a little like Barca. Or the striker needs to be a complete one, is strong, who can hold up the ball to bring others into play, can head the ball well, has pace and takes the chances when they come. Drogba, Torres (in the old days) or Van persie are masters of this.
4-4-2 needs one defensive midfielder who will be a work horse, cutting out passes, tackling hard but fair, winning the ball and then making simple passes to the players who will create. There are two serious combinations available here, either to have a box to box player, who can also pick a pass, and has the flair to get past a player and create space in front of him. Dembele fits this role well. Or to have a deep lying playmaker who can dictate the play from further back, making short and safe passes to get out of defence when needed, not giving the ball away in dangerous positions or picking out long passes to the forwards, or wingers or will then cross the ball quickly for the attackers to score. Modric was perfect for this. Both these roles also give additional defensive protection. By playing 2 up front it allows the crosses to come high or along the ground, or you can clear the ball to the big guy to hold up the ball or head down for other players to run on to. Ade / Defoe could work well here.
If we are going to play 4-2-3-1 I think we need to direct the transfer funds to a striker who can play that role up front. If we are going to play 4-4-2 then we still desperately need a striker (maybe a young up and coming) but most of the cash needs to be spent on a creative midfielder.