The LFO control is pretty limited on the OB-6, as far as setting modulation depth. You only have the amount knob and the mod wheel, and both go to wild extremes pretty fast.
An OS update to at least let you tone down the mod wheel depth would be nice to have. Maybe by holding a button while turning the amount knob. Having different depths per destination would be nice, too (e.g. hold down F.Freq and turn the amount knob to set depth for filter), but that might be a hardware limitation.
I don't know if or when any more firmware updates will be issued for the P6/OB6 considering they've been out for 5-6 years now, but we could be pleasantly surprised.