Things are what they are and they are not what their not, Myself would tend to think you may be better off keeping the two floppy drives being that bios only supports a limited set of hard drives. You can do a lot with that system if you make the A drive a system disk and use the B drive for everything else. Don’t know why, maybe because most of those old drives built back in the eighties are all thirty-five to forty years old now and they are not reliable. Back twenty years ago that was the highest failure rate on them of the drive becoming stuck and you had to whack the machine to get it going again so cannot imagine what it would be like today.
Got a couple 1530 systems and they used a large 10 meg drive that took up the entire bay. At least by the time you got to the 1550 they were using smaller IDE drives and thinking about it maybe the 30 used a MFM drive but can be mistaken.
At least with the floppies you can have a 720K system disk in the A drive with Grid DOS, utilities and maybe something like DOS Shell but you are not going to be able to load anything beyond windows 3.1 regardless what drive you can fit into a 30, the 1550 came with Windows 3.0 installed and a remember swapping that out for 3.1 but don’t think I ever saw a 1530 or 20 with Windows.