Yeah why not, just get them all
The reason I suggested the 45mm is that it's relatively cheap and great for portraits amongst other things, the 75mm is a different league price wise. The 45mm is also tiny and not a hassle to carry around. The 12-40mm f2.8 is a great walkabout lens but wide open it's not the sharpest lens I've ever used, and f2.8 on m4/3 doesn't give the best subject isolation if that's your thing (which it is for me

). Therefore considering the price the 45mm is a worthy addition imo, even if it's not used a lot. Of course, this is just my opinion and it depends on what you intend on shooting
Then maybe something like the 75-300mm/100-300mm would be a good option, as well as a macro. Hmmm, wonder how much more of your money I can spend