I respect the effortposts, and you do have really fun and interesting ideas here, but these items have issues beyond balance numbers that give them trouble fitting in the game; the only exceptions to this (with asterisks) are Cyclone, and Legworker. This is a very boring sick day for me and I have nothing better to do, so I'm gonna write all my nitpicks with these items. I'm not gonna focus too much on the balance numbers because you can't really improve that beyond basic sanity checks without actual playtesting.
Breathless Escape
This is an awkward one, and for reasons you wouldn't expect. It also feels like you don't have a clear vision for what you want from this item. I think the main issue here is that it's a T2 item, and for characters with large stamina pools like Ivy and Viper, this would give you solid mobility and survivability for the low price of one T2 item. It would be very hard to find a spot where the stacks give reasonable strength without the item being a waste of space for characters without above average stamina pools.
- Having dash distance change with stamina would make movement clumsier, especially when you consider abilities like Alchemical Flask. Consistency goes a long way.
- How would dash distance be implemented? Would it increase the dash's base speed, or would it extend the dash's duration? If it increases speed, how would that interact with dash jumping, or abilities that preserve dash momentum like Puddle Punch?
- The item encourages you to stack stamina items, which would make the 20s passive less relevant. However, at the same time, having a mobility buff after gassing out would reinforce wasteful movement and stamina usage; basically, it's an item that encourages you to play worse.
- The 20s passive wouldn't feel good with your other item ideas of draining stamina. If you were to try intentionally triggering the buff and suddenly someone kills your last stamina bar, it wouldn't feel responsive even if you were at fault. Basically, optimal gameplay with this would be to forget the buff exists.
Cyclone
Honestly, I really like this idea. It would change the way you approach the map in a way that's interesting. The difficult part would be to implement the push effect in a way that's fun while still being a threat, and in a way that wouldn't just brick or trap certain characters.
Imagine using cyclone not as a bullet wall, but as a way to shoot around corners or cover. What if you could surf the push effect to slingshot yourself? This item might just be a horrible Pandora's Box, but the potential is there.
Ammo Harvester
Overpowered, and would be awful to play against. Bullet stealing would inevitably have the issue where it would be difficult to tell the receiving player that their clip is being drained without some kind of feedback/cue, but this game is already heavy on mental bandwidth; it would basically be more clutter for the fire.
- The +Fire rate, +Lifesteal, and and active effect would arguably make this at the level of a T4 item, but there would be no point in grabbing this over the other T4s
- It's a winners keep winning item, and bullet hose heroes are already eating well in this department.
Legworker
Not bad, this could actually work (obviously with some stat tweaks if necessary). The stats make it feel like it should be an orange item, but there's already an abundance of orange slidey items.
There is one potential caveat, and it's how slide distance works. It's a timer where sliding too long increases friction dramatically, and the timer is reset when moving down a slope or gaining speed (the slope part might be wrong; too lazy to verify). Items that increase slide distance just extend the timer before the friction penalty applies. Basically, stacking slide distance on hit might be jankier than what you'd expect on paper.
Kinetic Impact
I'm assuming that "disorient" is open to interpretation because having a stun like that would be horrendous. You can dash slide instantly with enough knowledge and practice, which means this item is effectively an Abrams jumpscare in a can. It's not as difficult as you'd think to slide into people; sliding gives excellent turning control, and you can always just dash slide into them point blank. I don't think having something like a minimum distance before it's active would work either, it would just give you a different problem to worry about.
Besides, you probably know by now just how cursed Valve hitreg can be; the monkey's paw may curl its finger with this item.
Snail Trail
This item would be awful to fight against if you put it on characters like Warden, Infernus, Shiv, Viscous, and so on. Also, it would have clutter issues much like Ammo Harvester. Maybe it could work if you just remove the stamina consumption? Also the stealing stamina part is just... way too much. I feel like giving an item this much things going on would give Yugioh a run for its money. Imagine playing with your newbie friend and they asked you what the hell an item does, and you have to thump a textbook onto the table instead of using 4-6 caveman words.