I wouldn't grant any bonuses or penalties. I'm going to assume the magnitude of the elemental attack is significant enough that those factors would be insignificant.
I would have to agree with this. The impact of the attack is near immediate. It's not as if the person were soaking wet and sitting outside in the snow and was slowly getting hypothermia, frostbite, death, frozen solid. Being soaking wet would certainly speed that process versus being dry. The Ice/Cold/Frost attack is like getting hit by a ball of ice in a snowball fight. Soaking wet or not, that initial hit is what hurts and does the damage.
However, I will say this; being the GM allows you to improvise. If the attack hit and did a minor crit, I would say that the target feels his clothing starting to freeze up and -5 to actions, or -10 if it was a severe crit. In either case, play off the crit results and add a bit of a penalty to being soaking wet. But from experience.... 99-E cold crit doesn't matter if you're wet or not... you're frozen solid, but quite well preserved.
Oddly, the Fire/Heat when soaking wet wouldn't have the same protective abilities you would think it has. I say this from real life experiences having grown up in the family restaurant for 21 years, then being a firefighter for another 13 years. The last thing you want in your protection from direct heat source is wet gear. The first mistake I made when I was cooking was trying to grab a hot dish out of a wok that had been steaming for 7 minutes. I tried to take the dish out with a towel to protect my fingers. The heat went through the towel and started to burn and I knew I couldn't make it from the stove to the counter top in time so I grabbed a towel and thought "water will keep my fingers cool enough to grab this." I wet the towel with cool water and grabbed the dish. The heat transferred through the water directly to my finger tips so quickly I burned the fingerprints off my fingers and dropped the dish. It was near instant burns.
The second incident was in a fire. The run off water from the fire had pooled around my feet and I had no idea. I knelt down to get a better stance and by applying weight to my knee, I forced the water through my gear and burned my knee in a matter of seconds. I fell to the side and put my hand down into the water and that soaked through my glove and burned my hand.
The same theory can be applied as was for the cold. The person is soaking wet and gradual heat is applied. They would be able to stay cooler for a longer period of time until the water dried up. However, when you flash heat water, it turns to steam and steam is hell of a lot hotter than water. Steam burns are what we try to avoid at all costs as it is vapor and isn't affected by gravity the way boiling water is. Water goes downhill. If one is properly protected, the water rolls off the helmet, over the bunker gear, down the pants, onto the floor. It shouldn't have a path through the gear to the person inside. Vapor seeps in anywhere, is hotter than boiling water, and does more damage more quickly. The poor, wet guy in the armour would be steamed like a lobster. The Fire ball may not have killed him outright, but being steamed to death would do it. And wouldn't you know? RM has a Steam Crit Table!!!
I guess the simple answer would have been: Add maneuver penalty for wet target/cold blast for freezing clothes. Add Steam crit for wet target/heat attack. The severity of the additional penalty being dependent upon the severity of the initial crit.
A-E Cold crit = -5, -10, -15, -20, -25 to actions
A-E Heat crit = Steam crit one severity level lower as it is a secondary crit, not a primary crit. An A-Heat crit shouldn't produce too much steam damage, whereas an E-Heat crit should produce a pretty severe D-Steam Crit.
