It would have been priceless to see Thaddeus Stevens argue that secession was lawful. If Stevens were to have defended Jefferson Davis, he would have had to so argue as directed by the client. Not to worry, Charles O'Conor had it covered and there was no way the government was going to take the case to trial.
[GOP] Much better [as Lincoln's choice for VP] would have been Hannibal Hamlin again or even Lincoln's first choce, who turned him down -- Ben Butler.
In his time of need, Lincoln could indeed, have sought Thurlow Weed, or even William Tweed.
"Spoons" Butler was only a petty thief compared to those New York Yankee big-leaguers.
In Lowell Butler studied at Lowell High School; he also established a practice of stealing items from rooms of the boarding house tenants while they were at work according to one of Butler's biographers [Chester G. Hearn, When The Devil Came Down to Dixie: Bent Butler in New Orleans (1997), pp. 8-9]. Hearn goes on to suggest that Butler's early proclivities were life-long:
Butler died on January 11, 1893, an immensely wealthy man whose estate topped $7million. Nobody has ever been able to explain how Butler, who came from simple means and spent the bulk of his career alternating between law and politics, amassed so huge a fortune (Ibid., p. 6).
Knowing that, would anyone ever have to explain? -- LOL!
In his time of need, Lincoln could indeed, have sought Thurlow Weed......
Knowing what he did about Weed, whom he used as a dirty-tricks errand-boy (e.g. in the days before Sumter), I think Lincoln would rather have paid him to stay out of town.