Some coaster brake hubs - those made for BMX bikes etc. had super big holes to accomodate fat spokes (sorry, I don't recall the different hole diameters offhand). Most of the Shimanos that you would buy new would have the "normal" spoke holes. Even the "normal" spoke holes are pretty large though. You can build those up with regular spokes, but you will increase spoke life if you take measures - I recommend using DT spoke washers under the spoke heads, which are made specifically for this purpose. I have built coaster wheels with and without this precaution, though, and both methods worked just fine.

Best wishes,
Dr. Hans