My game mode idea

Separate the ranged champs from the melee. Literally put them in two unattached sections of the map. Players respawn almost immediately and only slightly displaced from the action, so there is no reason not to fight at every opportunity. matches are super short, lasting only 10-15 minutes, so it's just a flurry of action where every player must stand by their own merits, without needing to rely on teammates because every champ is on relatively equal footing.

Pregame: You que up by selecting either range or melee, each team will have three of each, and you can only pick from champs of that type. Naturally certain classes aren't really viable, namely assassins, but they are still selectable. Hybrids on the other hand, transformers and kayle, are not. Some specific champs like Rammus (along with thornmail) and Darius would have to be specially tuned.

The map: The melee champs would be in a regular single lane. Minions are replaced with minion ghosts (or something), which can only harm or be harmed by enemy minions or turrets. It takes about five seconds after dying to get back to your turret, but killing an enemy champ underneath their own turret grants triple gold. The ranged champs are in just a big open field, about the size of nezus blitz's map, but with only a couple walls, and some brush. Two capture points will spawn periodically at random locations, and they won't be visible on the minimap until it's located by that team. For a trinket you are given a far sight ward. The exact nature of the capture points would have to be tested and based on how marksmen workout in these conditions . You win by securing enough objectives. Securing objectives also grants a bonus to the other side of the map. IF a team destroys a turret, a capture point appears in a fixed location on their side of the map, getting closer to the spawn location with each one. If the other team captures this point, then the turret will rebuild with partial health. Each time a team captures a point, it spawns additional minion ghosts for their side.

Anyways, that's just something I conjured up in my mind, if anyone should happen to read this, feedback would be cool.