You answered the first part yourself. To log time as a SIC, a SIC must be required by the TCDS or the reg the aircraft is operated under. Insurance requirements don't count. The requirements for logging SIC time are listed in 61.51, no where in there does it say you have to have a SIC type rating.

So you go the dual route. Also in 61.51 are the instructions for how an instructor enters training in the student's logbook. What's he going to put, "Pre-flight, normal engine start, taxi, T/O, enroute operations and nav, ILS approach and landing" 20 times? I can see the interview:

"So Mr. Pimp, I see you have 50 hours in a Bravo and it's all training. And in those 50 hours you never even got to the non-normals or emergency procedures. Our training program here at Sky-King Aviation is 6 sims and a check, about 14 hours total. Do you think you can complete our training if you had 50 hours in the Bravo and hadn't finished?"