Im not opposed to loading off a floppy to gain suplkrt for hard drives. i have real floppy hardware so i would much rather use an actual floppy drive.There were some hdd solutions for dos 1 on the early bioses but I think they either required a boot disk with a modded dos, or some emulated a floppy. Read about one system that split the hdd into multiple floppys and had tools to switch to them.
There were also lots of 'floppy emulators' As far as i can tell these are hardware ram drives. Would like to get my hands on one of these as well as one of the early hdd systems.
There were also ads for upgrade quad density drives, not sure how dos got on with them.
It's your system so it's up to you how you proceed but if it were mine (and I had the other later 5150s), I would try to trick it out with an external HDD within the confines of the first rev BIOS. Ideally with an original solution, but i guess you could always brew your own.
Emulating the floppy seems to be the place to start. I think smbaker or smbarker made a card that could emulate a floppy controller. His you could load disk images via a network. So that should work, but it could be made much simpler by responding to the correct I/O address and store a 160K floppy in an EPROM. Would this work? Is this a relatively simple card to make.