They really need to add some sort of additional space. Mules would be amazing or simply adding the option to buy (with in-game gil) an additional tab(100 slots) to each of our retainers. This way, people who need the room get it, and the people who don't care, don't need to get it. Best of all, the people complaining about more retainers being added won't have to worry. I'd say though, that it should only be an option if you buy at least 1 retainer first. (That way, they're making some money at least for the extra space.)

We need more space. That is the truth. However, not everyone needs room. If you make it free, think of all the potential wasted space that all the gil sellers are taking up. And all those people that level only 1 class and quit the game. This is why it'd be better to make it optional and through in-game gil. The option to give each retainer an extra tab slot each(100 slots) and 1 tab slot max per retainer (For now) would be a dream come true.