Charge $20 a month (roughly the same as $9.95 a month in 1997), focus on creating a world and MUD-level game complexity. Stand on the shoulders of giants and get in front of exploits (which were basically new at the time).
I feel like people are starving for this type of experience again, but forced to feed on the scraps (WoW and clones).
Mortal Online was one such attempt recently, but it wasn't enough of a playable world. And any time someone creates a hardcore MMO, it attracts almost only PKs (because there are so few hardcore MMOs). There needs to be a healthy mix of people, of all Bartle types.
I can't remember where I read it, but I believe Raph Koster once said something like "Nobody pays $9.95 a month to get killed repeatedly by another player". While that is true, I also don't want to pay 10 bucks a month to only win. Surely, there's a way to blend these experiences. It feels very similar to the OSR vs trad gaming schism in D&D...