I recommend FWB hard disk toolkit for large drives like that.
Step 1: create a small 10MB first partition which you set to not auto mount. This will contain the hard disk’s driver in those first sectors
Step 2: create a 1.9GB partition which will contain your system folder. This partition will boot just fine because the driver and this partition are within the first 2GB of data, a requirement.
Step 3: create as many 2GB Partitions as you want to fill the drive.
If you’re concerned about sector sizes and small files eating up the space with minimum file size requirements on a 2GB partition, then create DiskCopy 6.3 images on your 2GB partition which will contain the software you want to run.
The smaller the DiskCopy volume the smaller the minimum file size. You could do 500MB image files and the minimum file size would be divided by 4 essentially. Sort of like your own HFS+ way of doing things.
One could be for utilities and apps, one for games, another for word processing and office apps, etc. then you just mount the ones you want to play with. If you end up with spare drive space, just copy those to a backup partition so you have a spare copy in case you mangle something.
Just note that only the partitions within the first 1.99GB are bootable. If you plan on having more OS versions you could make 4x 450MB partitions after the 10MB one that each could be bootable.