Can a detail object in Master-Detail relationship be made master object in a M-J-M relationship (Master - Junction - Master). My opinion : No.
If answer to above question is No, can we have L1-J-L2(Lookup - Junction - Lookup) relationship and still have detail object in M-D to be L1? Something like M-D and then D(L1)-J-L2. If not, I may have to design my M-D relationship as lookup and have L1-J-L2 relationship for many-to-many set. . Please advise.