I wouln't mind the Onee-loli but I think it's fine the way it is now-
Also, wouldn't it be more effective if Fujiyama told Mamu where her boss is? Pretty sure Mamu can destroy that company and she can be free to play with Mamu all day that way (at this point her salary is so low it wouldn't matter if she became unemployed)-
It's funny because I started reading this thinking it was onee-loli, like with Mai-chan no Onee-san Shiiku Gohan.
As for the other half of your post, it may work but I don't think Fujiyama would be able to pull it off without getting destroyed too, given her track record and general bad luck.