Not a fan of this "aim on target / aim on the ground" idea. :-/
Concidering how often i click to attack in second when some freaking animation is happening and my cursor sudently aims at something entirely different ... or how often i have some problem with camera positioning and have to aim via turn order menu, wich would effectively remove option to use "aim on the ground" ... sry, dont like it at all. :-/
I mean its not bad ...
But i would just need some "more ensured" aiming metod if you understand what i mean ... toggle, "pseudoreaction" (something that uses reaction popups, but dont use reaction resource), setting ... something like that.
Rest of the idea is quite cool ...
Not really sure if elemental arrows actualy "need" damage boost ... but dont really mind it either.

Except Detonation Arrow ...
Im sory, but "pure magical power" still dont fit well with explosives to me ... things that explore should in my honest opinion do fire damage, thunder damage, and possibly piercing damage for shrapnels ... but i just can understand the meaning of Force there. :-/
And to be completely honest, i believe this change would also need Spellcasting rework ... since right now, even Cantrips electrify/freeze surfaces you are standing on. O_o
As long as Arrows work the same, it seems more fair than remove it from one, and leave it to another.
- Shoot on the ground : Create a very small area that auto apply +2AC to all characters (you can more or less apply acid to 2 characters)
I believe you wanted to write -2AC here?
