What is the best course of action?

Personally, I prefer maps in the style of Ice and Flame. Campaigns are interesting, but in my humble opinion, they should be implemented better through small or medium-sized maps. Large or very large maps should be reserved for the last and penultimate missions. Overloading them with quests, in my opinion, is also not a good idea – this is more suitable for separate scenarios. 3-10 quests per map are more than enough, in my opinion. But there is a problem with transferring progress... in all the amateur campaigns I've seen, the campaign itself is implemented through a set of maps, in each of which the player starts from scratch. Is there a way to bypass this? A partial solution is to start with a Sphinx or arenas (libraries). It was mentioned above about spells – a possible solution is some kind of rune that, when stepped on, erases certain spells... I would also be glad to see some of the Heroes 3 campaigns reworked for Heroes 5, for example, campaigns like Eternal Love. Of the factions, demons are interesting. I like the knights. The undead are also enjoyable, but they are difficult to balance depending on what the player will raise and how the creatures will transform. I don't like the mages – the battles are tedious. I also don't particularly like the dwarves. The Tower are neutral to me. The barbarians and elves – it depends on the map... sometimes I like them, sometimes I don't.