1) Every game ever created have some cheat in it, it`s just matter of time before some player find it, so it`s not fatal thing you found out. It`s just matter of why you do it ?
In KB-tL hero is limited to 30 lvl, so are rage spirits, so you can do this but only for some time before lvling up spirits. One other thing, spirit exp is determined by current enemy army on battlefield, so if you leave 1 tohrn hunter against your full army and spend 100+ turns to sacrifice units, resurrect, gather mana/rage no exp will come form all that time. And hero exp is already determined by starting enemy army, so it doesn`t matter if you start battle with 1 peasant or 100 black dragons, your heroexp will be same.
2) As i said above, you can start battle with only 1 unit, and then finish with full leadership army, but what then ? You dismiss all those units before starting another battle. And it`s as you say boring as f..k.
3) Hm . . . getting lina before 10lvl, i`m not sure it`s possible, but you need lucky james underground map for it. If you dont fight him, but pay him for map i guess it could be done at even lower lvl, and you`ll lose only 2000 or so exp, from battle with lucky james
5) Yea i get how it works, but it is easy against AI. With human opponent (as in HoMM hot seat, or any other multi player option this tactic wouldnt work 0.1% )
6) Ok, my bad, in KB-AP/CW barbarians are uncontrollable. As soon battle start, they just rush at enemy units and you cant do s...t to stop them, so no easy way to prolong battle and run around picking chests, or mana charges
7) Try it, there are many interesting combo/builds in AP/CW. If you lik tL, you`ll like AP/CW also, it`s great game worked with allot of details, and there are great mods for it. Give it a go
I just now checked lina.atom file. What mod you playing ? In original game file max lvl you use 45 rage, for 6 charges 3mana/3rage for 10 each, so you all time spend 45 rage to get 30 mana/rage from 3 charges. Later in battle your rage income is almost 0, so i dont think with only inquisitors you will be able to keep rage on max to do this for 200+ turns. Something in your game/data/data.kfs/lina.atom is changed, or you have file from some mod that changed lina`s skills.