I have done some experimenting. I want to first say that I do not fully understand the logic circuit involved in the amiga floppy drive handling, and this experimentation was done to learn. And in this I did find some interesting things that I want to report.
My experiment was to try to get an internal floppy drive in the amiga as DF0 and the Gotek Drive as DF1 internal. Thinking I could put it on top of the floppy in the A1200, and have easy access. I began by making a floppy cable that is straight all the way, but have two headers for floppies.
A cable that is main header for floppy port > Middle connector > End connector.
I also made a cable to hook it up as external drive according to this;
I expected the gotek to need a 74LS74 and 74LS38 to recreate the logic of an external floppy drive in order to function. However, it seems to do fine with just the SEL signal, and not using the MTR or RDY signal on the floppy port.
Hooked up internally, with gotek in middle and floppy on the end, I get DF1 and DF0 working. Though accessing DF1 (GOTEK) will spin motor on DF0 (Floppy). If I reverse the floppy and gotek so that the floppy is in the middle and the gotek is at the end of the cable, it does not work.
Having just the floppy (DF0) internally, and the gotek externally connected (DF1), it also works. Though with the same problem that motor on DF0 spins.
So it seems that the logic for external drive is necessary for the amiga, as far as I can understand it. Though the gotek might do without it it.
I hope that I have made some sense in trying to explain this, and that I have relayed the relevant facts as well as possible, and then I also hope that people who are greater wizards of the amiga floppy electronics can make some sense of what to make out of it.
Can we do away with the added logic by modifying the firmware of the gotek, or do we need the logic for the sake of the amiga? I do not know.