1 - it'd be nice to have a grappling hook. the verticality here is very limited, which it would help with, plus it's one of the more unique and fun movement options in the main game, and it is often overshadowed by other things in combat. I don't even think it would break much of the existing levels if it were added. Also, any game is better with a grappling hook
2 - sword small, not worth the effort most of the time, make sword big(i'd say~the size of hardmode ore sword would be nice)
3 - weapons are not very fun. It'd be nice to have smth for mage that allows you to spend mana to get good burst damage/AoE/debuffs/smth special(maybe aquired mid-run). I think good options would be magic missle, wand of sparkling/frosting, aqua scepter, vilethorn, poison staff, inferno fork, bubble gun/shadowflame hex doll, golden shower and crystal storm. Also, any of the summoner's sentries can be in this group too
4 - sometimes balistas are placed in an annoying way in the dark level 1 not givng you the space to dodge their attacks or shoot them with a gun. Yes, even if you use the sword they're annoying