Well good for you. It's not us being "purists" it's us wanting what's best for these fish. The funny thing about cichlids is things can be fine for a while then the killing will start. Getting them at the same time as babies makes no difference. Once maturity hits you may have trouble on your hands.
I did the same thing as you once. I bought a whole bunch of different mbuna and stuck them together. they did well for a while but once maturity hit it was a war zone. It was horrible to watch. They were constantly fighting. Once I stocked the tank better things were way more peaceful. I would much rather have a nice set up I KNEW would work out.
Yes there will be those out there that it works for but more often than not it doesn't work. Break all the "rules" you want, it doesn't make you cool. It's just sad that your fish may end up suffering because of it.
Also your yellow fin does have a lot of female qualities. The only way to know for sure is to vent it.
