Wouldn’t want to see it be more RPG than FPS, but would like to see more RPG elements and influence with it remaining action focused. Will also warn that messing with HP boost without a damage boost counter is potentially disastrous. Even call of duty had stopping power to counter juggernaut. For this could give hunters better damage on crits and general weapon handling (ads time, reload, ready and swap), and locks a cool down reduction. Locks in particular should be more ability spammy at the cost of less effective gun use. Titans could also have a recoil reduction due to heavy armor. Then move onto melee boosts for Titan and hunter give they have melee focused lore and some melee focused subs. Locks could also be given some kind of passive energy absorption from energy weapons and abilities to add to recharge rate or slight damage boosts. If you want to change even more of destiny, then could switch to the halo shield system, blocking headshots vs shields and giving the classes different shield/ armor balances with the locks being most shielded and least armored and Titans being the most armored and hunters be a good mix.