I don't think that you can flash w/o a FXE player/loader and the only one is freelauncher, because if there were other ones, you would need freelauncher to launch them. There is this JTag thing that Mr.Spiv can do, if you don't want to return/replace your GP32 (I reccomend it) you can contect him and send him your GP32 and 10EUR (he is somehwere in Europe BTW) and he will flash mutiFW for you, no freelauncher needed, but I'd just return/replace it after all this trouble w/ it.
EDIT: /me is GP32 Mania now!!!