While I agree with your assessment of the nuances of MTP vs. USB, and the lack of knowledge, I did not want to go into detail about the pros & cons of MTP/USB and confuse OP. The OP indicated a concern about the ability of his A.) operating system being able to use MTP, and B.) moving photos & music and wanted to address those issues only (both of which he can do easily). Correct me if I am mistaken, but he did not address a concern about being able to edit documents, "portable apps", and the USB car issue. While those issues are important to you, the OP did not indicate as much. I too use my phone heavily for business, in ways others do not, and have customized and tweaked it to suite my needs. His questions did not indicate him wanting to use his phone in ways you or I would. If his main hesitation/fear was the inability to accomplish those 2 things, then his concern is unfounded.
BTW, have you thought of using LogMeIn, Dropbox, FTP, to continue to work on business documents?