most of the people that consider the MMO a bad thing has a single MMO in mind.. World of Warcraft.
The first thing that could go wrong is that ... this world doesn't need just another WOW clone... expecially not one with the Elder scrolls name attached, and by some leaks sadly that seems to be the direction the project is going towards.
There are great things in the elder scrolls franchise that I think NEED to be in TESOnline
First is the freedom.
I already heard of 3 factions ... and only the mention of that makes my skin crawl already...
Elder scrolls is about freedom... so .. make the factions .. is all right .. just don't enforce them in any way.
Let us be free, unaligned... don't make a Default unavoidable war, with unbetrayable factions.
Let me play without a faction... when I decide to Join a faction don't put me in a constant battle 24/7 but let me choose wich battles I want to fight. And when I'm in a faction let me free to backstab my so called companions when they don't expect it.
End most of all... no classes... no istances... no raids... you should develop your character freely, you should explore freely, approach challenges the way you want to approach them... or the name Elder scrolls really has no meaning in this game.
Guilds...
They kinda disappeared in Skyrim. Don't get me wrong, I Like Skyrim... but TESOnline is an unprecedented occasion to make the Guild System of old really shine.
First of all .. we all usually become the guild master of every guild in the game... in a MMO only a single guild master should exist in every guild.
Let the players play their way to the top of the guilds... Becoming the Archmage should mean besting the archmage... not necessarily in a PVP environment, there are a lot of different things that can be done ... number of quests resolved, ammount of resources given to the guild, votes from high ranking members of the guild... or even a combination of all the above. The fact remains .. with the experience ceasing to be single player only .. having a high rank in a guild could really be a huge achivement.. something worth fighting for.
And .. a Thing That I always found Odd... how is that when I'm an apprentice I take quests from a Journeyman and when I'm a journeyman no apprentice comes to me for quests and approval? a System where I can give credit for a promotion to people with a lesser standing and make them run errands for me would be great.
and .. TESOnline MUST HAVE thieves and Assassins.
Make sure you can deposit stuff ... make sure you don't have a huge item dependency (actually .. you shouldn't have it anyway... I don't want to grind daedric magical weapons ... make us craft our own weapons and make sure that daedric equipment has a slim advantage over steel ... not an overpowering one)
This should be a Morrowind+Skyrm craft and resource gathering system meets Early Ultima Online (before trammel-felucca, insured and stuff like that)
If it will become a Dumbed down elder scrolls lore meets WOW playstyle I seriously doubt any Elder scrolls fan will consider this game ... they will even feel insulted by that game.