My notes on an early Paradise drive (taken from contemporary reports) are provided below. The one described by the OP sounds similar, but seems to use the floppy rather than serial port for data. The fact that it is not bootable on a Plus indicates that it does not support the Plus serial port for power o indication. A confimation that it actually uses the floppy port and a model description would be helpful so that I can update my notes.

Begins ** Paradise Mac-10

Paradise offered another variation on the serial external hard drive theme for 128 and 512K Macs. The drive has an external power supply designed to sit on the floor to save on desktop space. The drive monitors a 5V line on the serial port and switches on automatically when the Mac is powered up. It can be used on either serial port but the printer port is required if you wish to use the Paradise print spooler feature.

A volume manager utility is used to configure the Paradise drive for use with MFS. One Usenet correspondent reported that the Paradise software will work in conjunction with the Hard Disk 20 INIT to permit the use of HFS volumes. Later versions of the Paradise management software officially supported HFS whilst still using 64KB ROMs.

Note: the Paradise Mac-10 will not work fully with a Mac Plus or later because these models do not provide the 5V signal on the serial port. A serial port adapter such as that sold for the Thunderscan is required for the Plus. Also a 20MB model. ** Ends