Creating new boss fights?

[Aile~♥]

I wish we could determine how rare certain battles are.  If we could, I give certain battles different music and essentially have them be "area bosses" akin to what you'd see in Suikoden games.

You can.

Using a hex editor, I presume?

[Misery]

I wish we could determine how rare certain battles are.  If we could, I give certain battles different music and essentially have them be "area bosses" akin to what you'd see in Suikoden games.

You can.

Using a hex editor, I presume?

Yes. I didn't link because Role usually doesn't seem to be too keen on hex editing stuff, but in this thread you can find the details of how to do it (Teawater also linked it earlier in this thread).
Below is a quote from it:

These are the battle collections, as I call them, you can assign 8 groups to each map. Not to mention that in this data, you would be able to edit the likelihood a battle would occur, (You could even disable battles in a map.) As well as changing which of the battle groups are more likely to be encountered than the others.