I presume you guys are going to add the missing Sequoia mob (new to this whole thing... don't know if it's actually in yet?), and also give the rest of the Vek their Alpha and Leader versions where missing or where you find it fitting.
The Cactus wouldn't work as a Vek Leader, in my opinion. Firstly, it cannot move at all. It would be too easy a target and it would not be able to move to another position or target another building if it's current position or target gets compromised. And unless it already spawns in line with the Corporate HQ (which might not always happen, or sometimes there might be mountains in the way), it won't be able to even try and destroy it. As the Cactus currently is, it just wouldn't work as a Leader, unless it undergoes some drastic changes.
And I presume the Sequoia would be a unique Vek Leader, like the Goo boss from vanilla, which has no normal form and only rarely appears.
I'd say you guys should increase it's hp by at least 1 point (for a total of 3 hp), to coincide with vanilla mobs, like the leaper. It's damage is fine, it's just it's hp I'm a bit concerned about.
4 or 5 Health. 4 Move Points. 4 or 5 damage attack. Perhaps even increase it's attack range by 1 tile, since it's now a Leader. But I don't know if the Sprout should be made a Leader. This is just how I envision it's stats would look like if it were.
7 Health. Perhaps make it shoot more Copters onto the battlefield than usual, but keep the damage it takes when doing so the same (takes 1 damage to deploy Copters). It deploys Alpha Copters, obviously. This would set it apart from it's normal and Alpha versions, as it can now deploy multiple copters, like the Spider Vek. The reason I think the Bud is more viable for Vek Leader than the Cactus is because the Bud at least deploys other Vek onto the battlefield, who can then move around, attack the player and defend the Bud if necessary. This makes it much better than the Cactus.
Overall I think the Cactus is pretty weak, because of the fact that it cannot move at all (or am I misinterpreting it's description?)
At the very least make it have more health than it's normal counterpart. Normally, there's a difference of 2 between the normal and the Alpha versions of a Vek, with the exception of the Beetle and the Blobber, who only have a difference of 1. I'd say increase the Alpha Puffer's hp to 4
5 or 6 hp. Keep it's Move Points the same, I think it's fine just as is. Increase it's damage by another 2 points, since it's now a Leader. I also think it's attack range should be boosted in some way. The Puffer is like the vanilla Burrower. The Burrower has an attack area of 3 tiles, but lower damage, whereas the Puffer has a smaller attack area, higher damage, and creates a smoke cloud where it wants to attack. It's quite balanced, but I don't exactly know how you'll boost the Puffer to make it feel like a real Leader...
The Beanstalker is the Island's direct counterpart of the Beetle, thus it's stats should reflect this. Since it can push adjacent tiles away, potentially messing up the player's positioning and damaging them if they collide with anything, it's safe to say the normal Beanstalker is fine as is. But I think the Alpha and Leader versions should get some added damage to their attack to things they collide with. I mean, they might not have spikes and such like the Beetle, but the bigger they get the harder they hit, right? Maybe not a huge boost in damage, but just give it some consistent way to deal direct damage to the player. Or if you don't want to increase it's damage, maybe give it better survivability. Give it some armour, so it's harder to kill. That'd also do the trick, I think.
I think you should give it some armour. It's like a tree, right? So maybe it should have thick armour, to reflect the hardness of it's bark. Alpha and Leader versions could have further increases in health and damage, but I don't think you should increase the Gnarl's damage by too much. Perhaps you should rather give the Leader Gnarl an increase in the range it can throw it's rocks, rather than damage? Look at the More Bosses mod's Digger Leader, it can push it's rocks over much larger distances, but it's damage wasn't majorly boosted like you see with most other bosses.
IDEA on Sequoia boss:
I heard that the Sequoia tree (in real life) needs fire for it's seeds to germinate. Perhaps you could use this for the boss in the game. The Sequoia boss could be an artillery enemy. It burrows to a safe spot and prepares to rain it's acorns down on it's enemies. And here's where the fire comes in. These acorns could be on fire. They set tiles on which they land on fire. So if the player manages to evade the acorns, they set a big area on fire, encouraging the player to kill the boss quickly. And since the boss immediately burrows back underground whenever it takes damage, the player has to be quick and try to one-shot the boss. Another thing: the Sequoia, like the Gnarl, is a tree, and it should maybe have armour to represent it's thick tree bark. This would make it harder to kill the boss, but I'm sure you guys could figure something out.
Thank you for reading my post. I hope you guys found at least some of my ideas helpful. Cheers!