Having it as a champ isn't feasible, that would unbalance it even more than a summoner did. Summoners bring power to everyone whereas a single champ release brings power to only 1 person in a game. So they would need a bunch of champs or the abilities which interact with the turrets would have to have a low impact which would be wasteful to a champ kit.
Otherwise, it is easy to make a turret interacting ability that is OP which means a champ which the entire meta would start basing itself around. Then the champ would be constantly banned or just nerfed into the ground as per usual, or both.
Maybe it could work, but it seems so hard to balance.