by design we don't want to have a 'replay battle' - the game is rather hardcore and challenging, so we want to go this way. But we are forgiving :) and we have the 'retreat from battle' implemented - so if the battle is hard for you, maybe it's better to retreat.. Also, if you kill some enemies before retreat, the next time you visit the same battle, those dead enemies stay dead. So you might think strategically here..
The ranged support is now treated as a mutator item - meaning you have to aldehyde and kill enemy archers, and then after battle extract this 'ranged support' mutator (it's 100% chance). Then you just equip our ranged unit and the support becomes available during battle. Shield ally triggers only when the 'protector' is not exhausted and also he must not stay on the opposite hex as the enemy - that is a weakness we think it's fair (also enemies have shield ally abilities and they use it often).
The upgrade of abilities - something we currently work on :)