Yes it is indeed possible to create your own ROM programs and setups. It's
simple to do. All you have to do is create a file which contains all the
objects that you want, then call up the Install Objects routine from the boot
loader (documented on pages 2-6 & 7 of o the manual) and select that file to
install.

However, the tricky part is that you have to remember that every object you
want to have in ROM must be part of that file. This means that you must copy
all of the sample header and keymap objects into that file along with the
programs and setups you select. You also need to make sure you include,
Intonation Tables, Pressure Tables, the Master Table, etc. To accomplsh that ,
you have to save each ROM object into RAM. One way to make this easier (instead
of having to save each object, is to load the ROM objects file that comes with
the instrument into RAM, then edit it and make any changes you want to the
programs and setups and save it back to a disk.

As to your other questions:

Both the KB3 and aLive Mode features will be added in v3 of the operating
system.

Version 2 does indeed support 2 gig hard drives. (This was added in v2, the
previous limit was 1 gig.)

As to the backup issue, the K2500 without PRAM is able to backup larger drives
than the K2000 without PRAM, but I am not sure if it can back up one drive
larger than 1 gig to another drive larger than 1 gig. I will look into this and
find out.