Just thinking about doable things that could be implemented in-game to make things more interesting:
I got the idea from razordome event and danger simulator, what if there were maps that allowed your heroes to ‘circle’ the enemy, like an arena. Danger simulator is already a semicircle, so what if enemy is in the middle facing all directions, your heroes could be more spread out? Or the other way around, and you have to be defend from all directions? This obviously wouldn’t work in PvP because of team imbalance, but I think that it would be great for co-op or campaign.
Different campaign mission types:
One of the things that ward me from campaign is the fact that most missions are the same - 5 heroes, 3 waves. What if there were missions where you could only use a specific type of hero, eg assassination missions where you have to use a rearline hero or a hero with a sniper mission, and you had to do it solo. Or scouting missions, where you have to play in pairs or triplets instead of 5.
Like in danger simulator where shooting barrels will blow them up dealing damage, what if you could use environmental things to damage opponents? Like in Sewers PvP map you could shoot off a sewer pipe which splashes sludge that slows enemies down or staggers them in an area?
Also the already-mentioned hero synergy and item trading, hero synergy would be a good concept but might force people to play with heroes they dislike, item trading would be HUGELY useful, as later in the game you start hoarding massive amounts of unneeded gear (like 2k+ green bio canisters). While quickwin tickets confused me for a bit, I think get it. You’re meant to play campaign missions manually, using quickwin tickets gives you the privilege to quickwin and not play the mission.
That’s all for now, if you guys have any ideas it would be interesting to hear your thoughts.