They should focus on the same thing they focused on for ACB.
Encouraging a BALANCE between the different options. They shouldn't focus on one aspect to the exclusion of all else. Or one element in preference over the others. If a player is good at something, they should have an option which lets them focus on that element of the game and be rewarded for it.
I'm not necessarily saying to bring back Brotherhood's mechanics.
Just that Brotherhood was better at balancing stealth vs. speed than ACR was.