I generally don't play these as much as the regular character or other variants, with a couple exceptions. They are a basic idea for variants, but they do work, and being basic isn't a bad thing really. One of the main reasons I like variants in GW and GW2 is how variants can have such different looks and effects, something that was sorely missing in BfN. I'll mostly be speaking from the GW2 perspective here.
Armor Chomper: This one got some alterations in GW2, but largely for the worse after they lowered his health and his bite effectiveness. Never had a big issue with this guy as even with his older, nastier bite and higher health were fine. It's a variant I play fairly often although I don't play Chomper that much.
Iron Citron: Love the metallic sounds and the way his weapon releases those large shell casings. In his normal form I find him alright, but he's mean in Iron Mode, and devastating against large groups of AI. Not sure if he would a nerf in a new game, but wouldn't be that surprised. Not my most played Citron, and I play Citron reasonably often.
Jade Cactus: My favorite cactus from GW, with Zen becoming my favorite in GW2. Leaving the needles behind like mini mines is quite useful, especially against AI and objective modes. I tend to use her more at mid than long range, partly due to her weapon and the extra health is nice.
Metal Petal: Her sound effects are great, her reloading has that metallic effect that's cool. One reason I liked Sunflower so much in GW and GW2 is her greater speed, something that really hurt BfN was taking different speeds for different characters away, so she's my 2nd least played Sunflower (Mystic is least), but i play Sunflower a lot, so I do play her fairly often.
Petrified Cactus: I vastly prefer Jade over this one. Looks cool for sure, and she's the least obnoxious manual detonation character, but still not one I really like to play much. I don't see her all that often in PvP matches either.
Rock Pea: Despite his loss in speed, I actually play him more than Electro-Pea or Plasma Pea. I'm not a fan of the speed loss, but he's not as annoying as E-Pea, and I'm not a big fan of charged characters, not saying they're bad, just that I don't like them all that much. The rock effect is well done on this one.
Roadie Z: This guy not only has more health but totally changes up the Engineer playstyle. I don't play him often for the same reason I don't play Chemist all that much (the short range), but I can't deny they did a good job on his presentation with the speaker effects and sounds.
GW upgrades were random via packs and automatic, so like you post, we don't have a lot of choice there.
In GW2, I don't use the health upgrade often, in fact I only use it on Vampire Flower and Count Chompula right now as that takes advantage of their vampirism.
Hardened in BfN got nerfed, but it needed it. It should only apply to the Oak and not the Acorn as well, or just get removed. I love Acorn, it's my favorite new plant, but being so small, having a weapon that's actually very good, and the 2 dashes means they really don't need extra health, even if one could argue that they are nuts so could have a hard shell. If BfN had variants, having a larger nut with more health and slower (coconut?) would make more sense and could used in the next shooter.
