Sounds mostly like Droopy's mod plus flashbangs. Making the enemies shoot full-auto only (when available) seems to make a big difference in their accuracy at longer range. It's what Droopy did, what HU does, and something I made sure Cloak-and-Dagger retains. It's also what I plan on doing for Blood Oil Remastered when I finally decide to go work on it.
As for the fixing the kit icons and names, shouldn't be hard to do. HU should have all you need when it comes to the kit textures and then you just need to edit the strings.txt file to make sure the right names are used.
Sounds can be sourced from a variety of mods. See the "Sharing is Caring" list for lots of stuff to work with.
As for any weapon balancing, not sure what exactly to do. Just try to make sure that tactics are emphasized and that you can't point-and-click your way out of mistakes too easily. Could do what HU does and have NPC versions of each weapon then make sure the enemy uses them. Since it doesn't sound like you want to add new weapons, this avoids the problem of having too many weapons with scopes that messes up the balance with how this game plays (one of my critiques of HU in the weapons department).
After playing SWAT 3 recently I've noticed that my most used mod for it is Finn McCool's Enhancements 1.5, a lightweight (only 700kb at induktio!) mod that mainly corrects errors found in the game's texts, enhances the sound, adds AI improvements from other mods, improves on the effects, and rebalances the enemy AI to be less superhuman.
So I thought about doing the same thing! The features I plan on implementing are:
Renaming weapons/items to their actual real-life name. This includes the grenade, whose in-game model is that of an M26 yet its HUD icon is that of an M67.
Fixing typos and/or inconsistencies with the mission briefings and audio if there are any.
Adjusting enemy AI accuracy to be less "aimbotty". Biggest problem with this is that it might make the game too easy, especially since I don't plan on removing the fog.
Changing the weapon sounds. Easy enough to do but whether the new sounds are better or not is largely subjective.
Things that I may consider:
Adjusting weapon balance. May have to be implemented due to point #3 in the above.
Adding new weapon kits. I have my eyes set on Burner's flashbangs if I go ahead with this.
If anyone else has other minor quibbles that they'd like to see changed I'm all ears.
Bit of a pity. Even with the updated UCP in HU they still look like regular grunts rather than a CIF unit with more funding.
As for the fog on the CENTCOM missions you might want to consider how that'll affect the balancing.
I could try to make a hostage rescue mission of sorts for you. It'd have to be a repurposed map from vanilla or another map pack since I'm not a mapper. My first thought was the Tbilisi map with the bank and embassy.