i have a few ideas.
first off don't release it at the same time as the star wars constraction sets if they do it will surely die quickly.
second off put an emphasis on their characteristics make stormer a rough grizzled hero veteran with a butt load of battle damage armor scars and maybe a prosthetic limb or two. give him a history of losing all his teammates due to a team members betrayal.
third let death be a thing don't be afraid to kill a characters every now and then just make it a death worth dying. less jul'mdama from halo 5 more like the noble team from halo reach. don't be afraid to kill off nameless heroes to show that no matter what they can all die on any mission at any time but trough team work they can survive to tell the tail.
fourth no gimic builds please that was bionicle's thing.
fifth go crazy on the villains. make one a mad scientist that cuts up heroes to make zombie heroes. make corroder a psyco that wants to go on a hero genocide make the villains feel deadly.
sixth get.......greg...........for............the..........story...........nuff said.
seventh make each set look different yet similar to each other and make the villains different so they don't come off as heroes.
eighth wait till like 2020 to launch HF G2.its would be to soon.
that's all I can think of.