My main focus isn't so much on balance changes, more so performance and stability improvements first.
That said, assuming the server performance is in a good and stable state, I'd probably look at adding quality of life to either the points plugin (like allowing a buyable ammo refill for the whole team, or a set of boomer goggles for the whole team), or other aspects of the game, like the 'worldmodel turn rate fix' plugin I posted about in the L4D2 section.
If those two areas of focus are in a good state, then I'd look at balance and actual gameplay changes.
Of course, I'd want to hear community opinions regarding balance changes - so I'd probably propose my ideas and gather feedback prior to changing things.
My general philosophy for L4D2 versus is that the game should be fun from all perspectives, regardless of winning, losing, survivor, or infected.
There's a couple tweaks I made to infected messing with my local server, such as making smokers more of a threat by increasing their survivor pull speed and reducing the latency of the tongue, or increasing the damage a boomer does when it scratches a survivor (they should be kept at distance 🤓).
Stuff like that is what I'd be looking for community opinions on.
Another thing that I think would be interesting would be setting up a fast download file server and have it linked to the game server, which essentially enables custom content to be used on the server and all players would automatically download it when joining (FYI - I have proven it works as a concept already).
E.g. custom sounds (like a radio playing to all players), weapons, maps, etc. - lots of possibilities there, but more of a back-pocket idea for now.
One more I almost forgot about - stats and stat tracking.
I know source stats was used previously for GC, and I've experimented with reading and writing stats to a database in my local server.
I did actually get it working, and I could track as many stats as I wanted, enabling things such as 'personal bests' for round performance, or time to earn a certain achievement, for example, and could even track stats by map, if desired.
Players would be able to check their stats in game in real time, and track their development over time.
That's all I can think of right now.
Let me know anything else you may be wondering, or what your thoughts are!