They actually prefer a post for specific ideas, as it's easier to organize. Course, if someone else is already talking about an idea, they'd also rather you add to that rather then start a new one for the same reason. 
--I don't like how the sovereign can die and then go right back out and attack a mob the next turn. I used this to cheese some units near my city just charging them over and over again as they were not healing in between turns. I'd like to see some kind of city add-on that is early in the magic research tree that is basically called 'Rejuvenation Chamber' or some such where if you die your sovereign's body is teleported to the chamber and it regenerates over the course of 5 turns. When he comes back to life he should only have 1 hp - and should also lose all items and gear that were on him when slain. If no chambers exist, game over. Before it was too steep of a penalty, now it is far too soft.
This could be fixed just by your second idea: come back with 1 HP. You'd have to stay in town to heal, and that would reduce the graveyard zerg effect you can do now. I don't think a required research is a good idea, you could lose a game very early before you have it just due to some bad luck on a monster spawn. (Especially for magically oriented Sovereigns who are weaker in combat and early game don't have spells unlocked yet.)
--It is probably too early to comment on this since magic system hasnt really been added yet, but I am concerned about the scarcity of magic crystals. What if I plan to specialize in fire magic only - I find blue and green crystals, but the only red ones are deep in enemy territory - I am probably doomed to defeat. Thing about master of magic was you got magic from any node which would power all spells. Maybe you could have something in the magic research tree that allows you to convert a magic crystal from one colour to another - though it should probably take 20 turns or something to do.
Definitely a concern, but I'd wait and see before worrying about it. Maybe they already figured a way to fix that. 