For the tack shooter, I don’t see any need for changes. Either on itself or the specialty upgrades that already exist. I actually came to know that the tier 3s are bizarrely equivalent to each other. Both in cost and usability, but still excelling in their own niches
So, I came to some ideas for their 5th upgrade
“Incinerator”: The left path side of it will give the Ring of Fire an extra attack that’s similar to a short flamethrower. It will do 15 damage at the same rate of attack as its fire ring(Basically adding back the damage from the tacks it had in the previous upgrade as one attack made to give it the single target damage it lost when upgrading)
“Shredding Blades”: With launching mechanisms made to properly spin the blades, they now shred Bloons they pass through, doing 1 extra damage for every 0.1 seconds they spend passing through. This also applies to the ability(This might be weaker than I imagine, so an alternative on the function could be that it turns the piece it still has into damage upon the Bloon it’s hitting. So, since with full upgrades it’d have 3 natural pierce and 4 every other shot, taking the max for the example, the first Bloon pierced would take 4 damage, the second 3, the third 2, and the last 1. And in the case of the ability which has infinite pierce, all saws do 4 damage)
I also found another small bug. The targeting spot on ZOMGs seems to be way too far on their back, causing towers to attack it weirdly in some situations