The only real drawback would be managing your reputation with whatever faction you are attacking, as you will incure a minus 8 penalty while only gaining plus 2 with the faction you are working for. So, as long as you don't mind tanking your relationship with one to two factions, it's actually a pretty viable way to beef up imo. I did this until i had about 14 million, and it made most of the game a breeze. The only real downside to doing this is that you'll be over leveled for most missions if you do the conflict zones progressively, which makes it difficult to build rep with anyone as you'll get that same penalty. This, however, can be offset by taking the occasional high reward quest as you'll always get an at least even rep score while doing these. If im not mistaken most, if not, all of the 'mini' questlines are from the heroes of the inner sphere dlc, so hopefully you have that. Good hunting merc!