Well perhaps we can create throwing potions with alchemy since it now a Stealth skill, there was mentioned before thats Skyrim have flammable oils in such cases throwing bombs can be done
You can shoot a fireball from your hand that explodes.
Well you are thief thats doesn't spend half of his life on studding arcane arts, but live at streets and work on Thieves Guild, there is two way to achieve powerful magic enchanted items and scrolls, but as Stealth skill Alchemy must be fortified more then just with poisons, flashbang grenades thats paralyze and stagger, sleeping gas thats drain fatigue and put into sleep, equipment damaging acid what does damage overtime, smoke bombs thats negate light in area, flammable oils thats increase fire damage and add damage overtime, there can be many options to make alchemy equal to magic
Besides magic can be silenced, reflected, dispelled, until spell is not powerful enough but well placed flaming oil flask can be only resisted
As well throwing mechanic isn't hard to be done I think marksmans must not relay only on bows since mages not relay only on fire balls and warriors on swords they have more options, I think marksman roleplay will be much less generic then it was in Oblivion.