The Union is only necessary in major sports because each team is owned separately so there are a group of owners. This creates a regular market, however the team owners historically colluded to gain an advantage over the players. As a result the players needed a union to protect their interests against the owners.
In contrast, there aren't owners establishing teams in e-sports. Each game can't be considered an owner just as you can't transfer a basketball player to baseball. There really is no conflicting interest for the owners, such as riot, as they're not interested in trying to make 1 team win. They want a fair, competitive, environment for all participants.
Creating a union would lower the gains in the industry unless riot starts taking advantage of the players. In general, unions/monopolies/non-competitive markets are BAD. They should not be entered lightly, only when situations demand it.
If you're looking for help for your paper, a union such as the ATP (professional tennis) is a much better example of what could succeed. In this case, the union allows tournaments to be held if they meet certain prize criteria and facility conditions.
At first it might appear that this doesn't work for league, because riot is the sole owner of the rights to host league tournaments and hence a player's Union couldn't do anything. However, if riot considered changing their business model to sell tournament rights to other bodies, then the players could establish a union similar to the atp to ensure tournaments were high quality.
Overall, I think unions aren't necessary in e-sports because the game designers are not like traditional sport team owners. They don't have a sole goal of profit from their team and could care less about the players or the sport, by definition they have a vested interest in the health of the sport and the pro players are an essential component of this. All a union would do is charge fees to players without providing much in return.
