Originally Posted by veganbikes

I am assuming this is a homebrew product because it is unlikely any major e-bike manufacturer is going to have a coaster brake on their bike even the cheapest e-bike cruisers usually have a rim brake at least which is also not super suitable but much better than a coaster brake. I would potentially look at something else that is a good candidate to convert to a electric bike if you really need to do that or get a pre-built e-bike from one of the many established companies using a high quality system like Bosch, Shimano, Brose, Fazua, Mahle...Hydraulic disc brakes are the ideal and are easy to mount on a lot of frames these days and can be had relatively cheaply for a decent set from Shimano or Tektro if you are building from frame up.