Will the neoprene jacket fit on a Brewmaster Bucket (since it has a thermowell already on the side)?

Yes.  

You'll need to make a very very small incision on the neoprene jacket where it rests against the thermowell (in other words, just cutting a small slice with an exacto knife will allow the protruding part of the thermowell to stick out through the hole)  This is very straightforward and should take all of about 10 seconds.