If you won't use it, then I would get rid of it. Otherwise, it just becomes something else that you will have to clean and, depending upon the dimensions, cleaning around the base of a free stranding bath can be a challenge. This may also allow you to have a separate enclosed toilet, double shower and/or double vanity (if you don't already have those), which may offer more practical benefits than an infrequently used bath. If necessary, possibly consider upgrading the bath in the main bathroom to a more luxurious size so that if you do feel like soaking in the tub, that option will still be available.

it's time for this bath to be retired back to the paddock...post a plan of the bathroom including measurements, size and location of doors and windows to invite suggestions for an upgrade

I think you have answered your own question in your comments. Unless for some Australian standard you need the overflow, I would just install the standard plug.

Hi, unless you take a bath at least once a week I'd skip the tub. I'd rather enjoy a bigger walk in shower, which is also a lot safer than climbing into a tub to shower. If you have the space instead of a tub and shower I'd consider a double vanity to give you extra storage space. It's a little luxury you will come to enjoy when everyone is getting ready on the morning.