I'm a strong advocate for your cause, since I tire easily of the repetitious battling alongside MultiZons, PoisonNecros, and WW Barbs. However, I'll explain some issues with your current list.
Spearzon nobody uses them,but I think it could be a very good char.These were buffed just this patch with some very strong weapons at level 75 and 95. I think until those weapons are more common, we'll have to wait to see people experimenting with spears.
Fire/Cold Bowers.... Nobody Uses themGah, yah I hate this too. They're supposed to be pefectly find builds. I've even played a Cold bower a couple of years ago but got bored of her because she was just way too strong (you shouldn't be able to launch 1 arrow and a cluster and clear the entire thing). I haven't done enough testing with Immo arrow to understand why it isn't popular, the patching effect should be just as cheezy against bosses at Meteor, but maybe the patches don't last.
Fister.. Actually Fist of Heavens is Magic damage in HU, so there's no specific aura you can use to help your damage. FoH is godly against undeads (HU has a lot of these), but so is BHammer. Anyone who's maxed synergies for FoH will have also maxed the skills for BHammer (which costs less mana, does more damage, ignores both demon and undead res instead of just undead (the FoH main strike ignores both I'm told, but not the bolts), and hits more targets when you're surrounded). It's hard to justify FoH unless you're a healer that needs to stay back from the crowd. I agree that FoH needs a healthy buff to stand toe-to-toe with sometihng like BHammer.
Vengance Pal's can also be great with some improving.This is debateable right now. The current standing is the Vengeance itself is flawed, having a relatively slow max speed (6 frames I think, so 4 attacks per second). Avengers need a massively high damage weapon that is also very fast (this weapon is sought after by everyone, so is very hard to get). Avengers can't leach well, and HU does have some pretty hard-hitting critters (this isn't a great argument though). Currently,
Convictors are getting some interest, since they can make use of exactly the gear that other people don't want, and they make use of it very well.
Conversion is the Stupiest skill..needs to be changed.Sorry, but many would disagree with you, and I would personally advocate to keep Conversion at any cost. For a low-HP "tank" like Paladins and Assassin, the ability to bring the enemy onto your side is godly. Not only are monsters the best tanks, but you can get great abilities from them like 1000HP Prayer (A3 healers), Amp (succubi), Lifetap (Minotaurs), Might (shamans), etc.
Fire Druid (No Fire Claws, but Pyre Fire Druid)These already exist, and are already shown as a little overpowered. They might have been reduced recently, which is why we're not seeing them, I don't know. Also, no one was using FireElemental druids, so I made one, and then saw another guy testing them, so maybe that's why you think you're seeing only those around. FireElemental druids are quite weak, although FireStorm is less weak (keep in mind that FireClaw druids have well synergized FireStorm). Since both FireClaws and FrostBite are capable of 2 frames per attack, these builds are ranked amoung the highest dps builds in HU.
It could be Great if we got more builds avaliable.I'll always agree to this. Here' a
thread I tried to get started a couple months ago. Sadly it never went anywhere.