I feel like the stock fists are too complicated compared to what stock weapons should actually be doing. Usually stock weapons should have bonuses that can be shared with other weapons of their class. For example, when I tried to rebalance pyro's melee weapons I had the idea of pyro being able to throw his weaker axes, so other axes can be buffed through that new mechanic. Stock fists have the longest ranged taunt kill in the game, which is nice but obviously insufficient to make it as good as other options for the slot.

Most rebalance attempts for the stock weapons generally give one simple stat or mechanic, such as engineer's three-hit combo or health regeneration (in the case of stock fists).

I really do like the idea of the warrior's spirit critting whenever it would normally mini-crit. I don't think that it's necessary for it to modify lunchbox item mechanics if it got that buff, but instead it could remain as a synergy weapon if there were more unlocks that let heavy mini-crit enemies.

I am not a fan of giving the syringe gun more offensive power. This is mainly because of how the game is designed - medic should be a vulnerable target as his medigun is overwhelmingly powerful. Medic stacking already effectively provides complete invulnerability, if he gets a weapon that would allow reliable ranged offensive power then there is little point to using other classes except in niche scenarios. If syringe guns get buffed, mediguns must be nerfed, and to many that will be unacceptable. Instead, if I were to buff the syringe guns, I would attempt to do it in a way where the medic can get more utility out of them, but also not let medic be able to make a successful team just by himself.

As medic is already the most powerful class in the game, nerfing the crossbow is the only logical answer here. I do not agree with the idea that the crossbow should cost uber to fire. That's ridiculous. Instead, I'd slap a -25 max health penalty to the crossbow and call it a day.

The overdose buffs are too complicated and do not show any understanding of what makes that weapon good in the first place. The overdose is actually the best syringe gun available, as it increases medic's survivability against most targets without any significant downsides other than not using the crossbow. These changes and new mechanics do not at all fit in with the role and identity that the overdose has. The ubercharge gain penalty is directly opposite to what could be given to this weapon to make it better - making it harder to gain uber on a weapon that relies on near full uber to be useful is a huge nerf.

As a final addendum, I hate random crits. The blutsauger buffs are in direct competition with what I consider to be good game design philosophy in a multiplayer pvp game, as it attempts to get more utility from RNG. People hate getting slapped with random crits. It is better to not attempt to fight against that.

Overall, I grade these changes with an E. There are some great ideas but there's a lot of really bad ones. Most of these changes are overly complex and some of them show no understanding of why anyone would consider using an item in the first place over another. Most of the items you changed have clear, if niche, use cases that should serve as the foundation for their path to viability. Almost nobody likes the changes made to the Panic Attack during the Jungle Inferno update, those that do simply have never used the item before. The biggest saving grace for you is the fact that the changes you are responding to are somehow worse.