It's possible. You can edit the ItemPMT file for weapons and techniques damage and you can also edit the battle parameter file for monster resistances.
Attack type element is storm and 'burning series.
I change value those element in PSO BB PMT Editor ver.0.03 "Special Data" tab.
But I seem that this change not reflect in-game.
Whatever you change has to be placed onto your login server too... if you're using the old login server, needs to be PRS compressed and replacing the ItemPMT.prs