I had some ideas about the class/skills system.

I haven't gotten up there too high, but it appears to me that the skills you are able to receive per class are assigned to you when you reach a certain level. My suggestion would be to add more user-choice there. I know the whole sub-class thing has been done, but there's no reason that can't be made to stand out as well. This could go hand-in-hand with the alignment system I'm assuming might be incorporated.

Let's say you make an assassin. Fun stuff, you're leveling up, finding treasure, whatever you decide to do. Then it comes time for when the game would normally hand you "Claw". Instead, it gives you a choice between two skills, we'll say "Shadow Claw" and "Rogue Claw", representing evil and neutral or freelance alignment respectively, each having its own benefits pertaining to its effect on certain monsters or whatever. This is also assuming assassins cannot be "of the light" or of holy alignment, being sneaky theives of life. Those don't have to be the names, but something very obviously denoting which alignment the skill is following would be handy. There could potentially be different temples or locations where said skill is taught, so you have mentors of alignment. As you level, you could choose to follow one set of skills, or maybe choose to have knowledge from two or more temples. Your choice. That way, instead of you proclaiming an alignment from the start, your actions and choices as you move throughout the game will decide your alignment. There would be benefits to following each, possibly such as having a foundation in "Shadow Claw" would make your "Shadow Claw Frenzy" attack stronger. This would probably mean that paladins cannot be evil, notoriously being warriors of the light. Or maybe if they choose evil skills, they become fallen paladins or something of the like.

I'm honestly not even sure if any of that is possible to integrate. I'm just hoping it'll start some conversation on the topic. So what do you think?

How about each level you gain x amount of skill points.

Each of the different classes will have a guild, and a trainer.

You train your skills in your own guild for a standard amount of skill points, and you can train certain skills from other guilds at an increased cost.

This is a simple way to vary things up a bit, Meaning players can make things like a warrior character, Who also has a medium knowledge in the dark arts and so on.

If there is alot of classes it only enhances this, because you would be able to customise your character freely, rather then following a set path.

Giving the players a sense of ownership over their character would be a huge step in really developing a concrete member basis. What a lot of games have done to keep the older members interested is a second class option, or an extension of your current class. If that in itself doesn't seem appealing, I'm sure there's something we can do to it to make it more desirable for our intentions. Main point would be to make sure older members remain interested after they've experienced most of the game already, so there's always a goal or something else to be discovered.

What do you think of a second job/extended class?

I used to play a MUD called barren realms.

The way they kept people coming back is through a remort process and a redemon.

What would happen is, You would level up to level 51 and become a hero player, you would then play through to level 151 and had the option of becoming level 1 again as a special demon race.

Maybe something along those lines would help?

I think all of these ideas are great. Ive always like games that have secondary classes (Ive seen a couple with tertiary classes even) and that does open the possibilities for a player greatly.

I think one of the keys to keeping players involved is constant content additions. There really needs to be a great deal of attention paid to what the people want. Listen to the masses, give them what they want when feasable and they will be happy. If there are several people that are nearing the current max level or at the hardest parts of the current lands, and people observe them saying "man it would be great if they added ____ next!" Take it into serious consideration. Of course you cant give everyone what they want, but you always need to be open to anything.

It doesnt always have to be big changes either, even the smallest of changes can be great.

Another thing I think that keeps people involved in a game, is lots of alternate things to do. Something other then just questing, hunting, and mining etc. Something that maybe has no real affect on your characters gameplay, but can be amusing.
Ill use EQ2 as an example of a game with plenty of alternate things to do. Besides the main quests and hunting, there are also collection quests, which involves fining items on the ground and adding them to your collections. Once you completed a collection, you could turn it in for exp and usually a pretty nice item. Lore & Legend quests which involve finding a book somewhere about a certain type of creature (ie Goblin) which starts the quests, and then you have to kill them to "learn" about them. Once you have gathered enough body parts from them and studied them, you get exp and a tropy pertaining to that creature that can be placed in your house.

There are lots of things that can be added for people to do.