Other than that without the Cromwell restrictions he is an ungodly king of vampires who should have the power to make D into a familiar. His regen isn't really "regen" but soul based rebirth, and then at the end it is quantam based re birth kinda thing so it's doubtful D could negate that.
If that stuff Reikai was sayin is true though, (big if) Then D could potentially tie this. He would have the speed to dodge most everything Alucard could through at him and if he has enough power he could kill him. Alucard would be back up in a second though and thats how the fight would keep going until Alucard gets the lucky tag and ends it. Im not sure how D puts Alucard down for good.
And who ever (Reikai) said Alucard doesn't have a habit of turning into a little girl is wrong, he assumes that form in Hellsing Dawn.