I think he would be a very good player for us, and we would legitimately compete for everything with much more confidence, if we had a player like Modric in our team.
Simply said, the only players who can ping the balls consistently in the way we play, which is with 2 deep lying playmakers, and now perhaps a #10 (Kagawa) with a central striker (Generally Rooney), is Michael Carrick, and Paul Scholes.
We rely on our DLP's to get the ball to the wingers, and to the #10/striker, because the attacking threat of our CM's is minimal. I like this approach a lot, as the 4231 we'll line up will be defensively more robust than last season, but rather more exciting and adventurous in attack, especially with a great creative #10 in Kagawa, and an absolute world class player to finish the chances as well as spread the play in a much less selfish manner; Wayne Rooney.
Modric can fill that hole next to Michael Carrick. Because Scholes can't play week in and week out. It remains to be seen whether he can even compete with top class opposition; against Spurs and City we struggled to keep the ball a lot of the time (10 minutes without the ball at WHL, and at City poor play), because his legs are just old. He can't cover that much distance, another reason why i think 4231 is better; Kagawa will help out to pick up Scholes workload.
With Modric, we would have a player that has brilliant technique in his shots, is a great passer of the ball with a great passing range and a good dribbler who can add a dimension by adding to our attack with more than just passes. He sprinted past our midfield a few times at WHL, and with a 4231, he'd have more license to do so, compared to the 4411 we played. Having 3 midfielders gives all of them a lot more freedom, whereas having 2 requires them to be disciplined, and more often than not, get dominated 3v2.
Modric can hold his own defensively too; and can run a lot to cover the distance etc.
He's also just a top quality player, and that's what you need to win.
De Gea; Evra, Vidic, Evans/Rio, Rafael; Carrick, Modric; Nani, Kagawa, Valencia; Rooney
is an incredibly strong lineup, with quality spread throughout the pitch. Our midfield and attackers are all among the top players in the world at what they do; a Bundesliga player of the season, 2 of the top 5 wingers in the world, a player sought after by Chelsea, United, and the Spanish Giants, and an understated Carrick. Oh, and someone called Wayne Rooney.
A young GK with the potential to become the best in the world, and brilliant CB's. 1 of them was consistently considered the best in the world till his injury, and another covered for him very well. Our full backs may well be the weakest point, yet Evra is from finished (I think he's essential to our play and his frailties are overstated!) and that Rafael can be a top player if he keeps concentrating!
Modric would be a great fit; if we can't get him, I remain optimistic we'll go for someone that can assume Carrick's role as a defensively sound DLP i.e. Someone who can pass at >87%, good passing range, and be defensively very good. Such a player would take pressure off Carrick, could sit alongside Carrick, and eventually replace Carrick i.e. M'vila/Martinez. Both are very good at passing the ball!
Obviously Modric fills the 'Scholes role' 'next' to carrick, but either type is good.
With Fletcher, Scholes, Giggs, Cleverley and Anderson with their respective problems (injury prone/age) we only have 1 mr. reliable!