Tested first loop with j.D and second loop without j.D. First, you still cannot link 5D to 236D. Second, the damage and Heat gain is between loop with j.D and without j.D. In conclusion, I would not recommend it. You still have less options and it is quite hard to perform it, since you have to start the j.D loop a little bit later than the j.C loop.
I'll add information on the j.B > j.C later.
EDIT:
OK, everyone is free to correct me if I am wrong, but it seems that it is not possible to connect j.C loop > j.B loop and j.B loop > j.B loop into 5C, because the j.B in the second loops kicks your opponent too hight, so that 5C whiffs. Take this information with a grain of salt, since it seems that the j.B loop is the hardest of the three (you have to add a little delay between j.B and j.C) and it is quite possible that I made a mistake.
However, the j.D > j.B loop connects to the second hit of 5C. It is likely that j.D pushes the opponent lower than j.C.
EDIT 2:
Regarding j.D > j.B loop; it is also not possible to connect 5D into 236D and the third hit of 6C whiffs, like in loop j.C > j.C.