If you need inspiration for what I believe your current audience would enjoy try looking at original Ultima Online, Shadowbane, and Dungeons and Dragons Online. There's a sweet spot somewhere in between those games that would both make truckloads of money AND bring years of enjoyment to your most loyal supporters.
First, I just want to say that I have faith in this game. Honestly, out of all of the MMOs in production right now, I think PFO has the most potential. I've heard recently that some things are going to be changing soon, such as bringing on board a new investor. I'm hoping everything will go good and the game will evolve into something so much more. I believe Paizo (Goblins Works) can make an incredible MMO that millions could enjoy. However, I would say don't look at the past for inspiration. The games mentioned above are obsolete. Since PFO is supposed to be a modern sandbox game, why not draw inspiration from upcoming sandbox titles and put your own twist on it? Games such as: Everquest Next (assuming that game is still in production...), The Repopulation, and Albion Online. I think one thing that is lacking in current MMOs is variety and choice. When I play a sandbox MMO, I want to feel that I can literally do and be anything I want. Adventurer? Mercenary? Hero? Villain? Entertainer? Diplomat? Bandit/pirate? Governor? Merchant/trader? I want all of those options available to me. Just look at the table-top game. So many choices! So many different ways to create characters. When I first looked into PFO and saw everything they were promising, it sounded exactly like what I would want in a sandbox MMO. Then I saw the game. And was completely let down. I'm thinking early enrollment wasn't such a good idea, but thats just me. Anyways, here's to 2016 and hopefully the redemption of PFO! I'm counting on you guys! Give me the MMO I have always dreamed of playing.