Any unlock a player gains should not be more powerful than an existing weapon. It may be more useful in different scenarios than a starter weapon, but not necessarilly be more powerful.
To make this work as a MMOG, you’d need conquerable outposts and cities. A player, upon creating a character, would then choose a faction to align with. Each faction would have headquarters that can be attacked, but can not be conquered. To conquer a city, your faction would need to gain control of say.. four of the five capture points within the city. If you’re within the area when your faction captures a city, that counts as a win. Players would build profiles online where their stats can be accessed and gain ranks and unlocks in-game.
Throw away death penalties and time sinks. I know there are masochists out there, but ultimately, you want the game to be fun the minute the player logs on. I think it is important in any PvP game, to be able to log on and get into a battle immediately. Players could form fellowships, or squads, and squad leaders could create moveable spawn points. Battle commanders could be elected in each area, depending on who is at a command station. If someone is commanding and a player with higher rank comes along and wants to command, they could force the other player into battle.
To summarize, I think a PvP MMOG should play much like a multi-player first person shooter. Emphasis on teamwork and tactics, without overly-complicated spell, item or skill systems. Don’t try to fit a FPS into the MMOG mold, but create a FPS in a persistant world.
People pay thousands of dollars, every month, to maintain FPS servers. Create a game that is appealing to them, give them thousands of other players to play with in a persistant world and add content regularly. If you don’t screw it up, you’ll do very well.
People like to compete. The learning curve is small. Some people will naturally be better than others. No one needs to be completely equal. There doesn’t need to be solo content, or NPC content, if there is always a battlefront. There doesn’t even need to be NPCs. But if there is, allow players to form squads and recruit AI soldiers to take into battle with them. This would allow players to form groups entirely controlled by them.