1. Seems okay. The only problem I have is, switching weapons on the fly isn't a thing. Having archers who are suddenly incapable of melee after getting one or two attacks off will dramatically nerf ranged attackers. Against stupid AI this isn't a problem, of course, but in other situations it might be.
2. Every direction? Then you can just deploy fast-moving, suicidal tackle units to shut a person down and prevent his armies from moving so they're pinned for your suckerpunch. I don't like it.
3. No.
4. Ranged units, sure. I run into a fair amount of spellcasting units after getting into the vicinity of Strong. The whole point of the game's post-apocalyptic backstory is that magic is rare, I thought. If everyone and their dog on the overland map can cast spells it interferes with the setting.
5. That's silly, because there's no situation in which regeneration's small healing is superior to taking an action that inflicts damage, unless the unit is crying in a corner of the map while the meatshields duke it out.
I do think it's absurd that Regeneration heals 1 HP per turn in combat, but only 1 on the overland map, however. Units with regeneration should, logically, be restored to full health each season. The fact HP comes back at a rate of one every 20 seconds or whatever an initiative round is during combat but somehow slows down the moment the adrenaline stops pumping to 1 per couple months was poorly thought out.
Increase the mana cost, the level requirement, or make it only castable on single-member stacks, but make it restore all the HP on the overland map. There's really no other way to balance it besides removing it altogether, anything else just leads to 'optimal unintended behaviors' like idling in combat for teh healz.
On a related note, Death's vampirism equivalents aren't even remotely as good. 3 HP whenever an entire stack dies for Rosoln, for example, is silly. 3 HP per member of a stack, okay. Killing a stack of 3 militia for a 9 HP yield is still downright anemic, but I'd take it. I'd prefer 5 or 6 HP per head. 3 HP for killing a 50-HP stack of soldiers, though, is practically useless in terms of sustain value. Add to that, Rosoln melee units taking advantage of the faction vampirism have no substantial Defense and are prone to getting whacked quickly anyway and you've got one of the most useless Race advantages. Ironeers and the Altar have it way better, to name a few off-hand.