So, I had an idea specifically for coop play only because i can see it becoming a balance issue on PvP.
The idea is that shotguns need to have a little more "on the fly versatility" and usability.
Firstly and most important of this idea is the reload. Anyone that has used shotguns in sandstorm will automatically know what its like to get stuck in a reload animation. So I suggest that there be an option, only an option (possibly in the settings), to be able to reload one shell at a time. (this can, i guess, be put into pvp?) The only other way to stop a reload is my clicking fire or switching weapons, which itself is another spiral down into failures.
The second less important part of the idea for shotguns is on the go ammo diversity. I think that it would make the shotguns more dynamic if you can carry like 5-10 shells of another type of shot. i think a way to be able to implement this into the game for shotguns without crow barring it in, would be by either making the option through a long press of a reload key or using the under barrel gadget key, considering the shotguns don't have any under barrel attachments.
The reason i suggest these is because i dont think there is a reason not to. with the recent update we saw rifles getting the skeleton key added to their choices. So, i think it would be cool to see a more dynamic styles of play added to the shotguns. You could even add breaching rounds that blow doors off hinges. Possibly dragon's breath to catch things on fire.
Again, I dont think a player should be able to have too many of these alternative rounds, but enough to add diversity into the shotgun play.