My general opinion on each of the topics. Feel free to elaborate as you wish.
Targetting - Seems to be a very decent system. I suppose it doesn't have too much use as you do not have to target someone to hit them. Still, it is a good way of knowing someone's name, and also for targetting in magic system 1. Plus, this allows people to have infamy for being skilled in the game. Overall I like it.
Stamina - I definitely like this system. I think it is important to have limitations on certain moves like sprint. Plus, stamina forces players to consider actions before they make them.
Combat Stance - My only worry about this is that the game will feel "clunky" when you enter combat stance. This was my impression of The Chronicles of Spellborn when I entered combat mode. Everything felt slowed and dumbed down. I hope that this is not the case in Mortal. I also don't want it to be too big of a pain to change stances. After all, my fingers can only reach so far on the keyboard without causing problems.
Attacking,Blocking, and Dual Wielding - I like this system. I expect that the delay is due to lag factor. Hopefully the combat doesn't feel too slow. I also think that duel wielding should be done as Catmorbid describes. Why not just make the RMB attack the right weapon since it does the same for blocking with a shield?
Hitboxes - Color me impressed.
Magic - This is obviously going to be the biggest concern of the community. I have no problem with the spell list only being around 20 spells long. After all, in most games you find that there are really only about 20 useful spells spread across the classes. I am not sure how I feel about the two systems described though. My heart wants system two for the skill aspect, but at the same time I want the number of spells to stay around 20.
I also think that PVE and PVP spells should stay in close proximity as usage is concerned. I want most of the spells to be "battle" useful. Especially since I now know that I will be able to play a Bard! You mentioned Music and I would hope that some of the music used would be helpful. It would also be neat if the music played different songs, but I don't expect that feature as it is fluff. Make sure the game has jingling keys first.
Heal spells are something that definitely needs to be addressed. If you use magic system 1 then heals will be rather easy to use. If system 2 is used then being a healer will be extremely difficult and tactical. I for one play a Bard/Healer type so hopefully it will involve a lot of skill. I don't want to just stare at my allies to do my job.
Mounted Combat - FPV FTW.
Fatalities - I presume this means you will be able to talk to everyone. I LOVE THIS. I expect the many players to beg for their lives before facing death. Luckily for them, Duncan Idalgo is a nice chap.
