[hinakatbklyn]

I had a mostly easier time picking the mostly main cast, but the other cast later on is much tougher to figure out. If I took a particular character you mentioned, took the seiyuu, matched him / her up to another character she voiced, my dub prospects would look like:

Aisa: Either Stephanie or Kari
Izzard:

Spoiler for another character another series:

I get it now. The seiyuu who voiced Kyon from another series also voiced Izzard. I admit I would of put Bosch in the role of Kyon rather than Crispin Freeman. If the seiyuu voices are similar, I would perhaps do the same here with Bosch. (But I would have to see that episode or episodes that character was in).

Motoharu and Maika, I would have much more trouble figuring out.

(Edit I found Stiyl so I have an idea who I would pick without using the seiyuu as a stepping stool.
(A) Vic Mignogna (If he's serious) (B) Patrick Setz

I'll use the same theory for Accelerator. I went with Bosch first without knowing about what he looked like. Now I have an idea of who to choose:
(A) Jason Liebrecht (B) Steve Saley (Cannon) Both young but energetic