Hi Pseudodiego,
Well, considering that increasing the damaging and protecting stats of the enemies (or lowering the party's) can be balanced by leveling up and longer battles, it wouldn't make the game impossible to beat. So you can do it like this if you want.
In Unleashed, another change was to remove the elemental absorbtion of the equipments and most of the elemental nullifications. This would be needed as well for an "Unleashed" experience since there are several bosses that are not a threat anymore with a proper preparation, even with boosted stats.