With the rollout of alliance wars and the need for 30 heroes minimum to fully participate, we need 10 free additional hero spaces. You only start out with 30 slots and this made sense when it was put in place but no longer. It’s fair because the game has changed and those extra slots are now essential as opposed to being a luxury to spend gems on. With how it is now, it’s nearly impossible to have 30 heroes and be able to level them adequately (specials), even at a high level (30+). Another idea is to add two additional slot increases as a level up reward before level 25 and give it automatically to those who’ve already passed that mark.
Edit: Additionally, to perform well, the heroes will need to be 4*+. So on top of needing 30 4*+ heroes, I need a team of 3* heroes with a bench for the events. There are simply too many needs in this game for hero slots and the current amount given does not reflect the changes to the game.