Make expansion hirelings (collector/ultimate) have an option for multiple levels.

Right now, when you want to summon one of your hirelings they are locked on one level, like Teal is 7.

My suggestion is to implement a pop up window, just like the one from teleport/spells, where you can select what level you want your hireling to be summoned.

Heroic hirelings will be available from lvl 1 to 19 while epic hirelings will be available from 20 to whatever the current/future cap is.

This will make expansion hirelings way more interesting.