Well, some good news on this actually.
I've done some more testing and it seems that it is possible to have an .ISO file without the ROMS included. My worry before was that during a scan LusSpace would check through the Super NES.dat file and enable + add the full path of the ROMS it finds. Anyway, I've managed to get around this...
With the .ISO file, the user would then just have to do the following:
... Download the .ISO file.
... Download all desired ROMS.
... Mount the .ISO and copy all the DVD's contents to the root of any HDD partition.
... Copy all the downloaded ROMS to "selected partition\SNES\ROMS".
... Launch the Front End, select Options --> Only Screenshots, then from under the Scan tab, click the button Start Scanning.
... Once complete, select Options --> Only Screenshots to hide this menu again.
... Exit the Front End.
Now all the new ROMS would have beeen recognised and you can burn the DVD.
I'm not going to create this .ISO for another week or so though as I wan't to get as much as I can in terms of functionality finalised first. Will keep everybody updated.