With all due respect, the founding members have ample experience in the MMO arena. In other words, they know what they're doing.
You can't do a story-focused MMO. It simply doesn't work, because all the quests and the backstory are lies. Kill a million rats, bring a million cures to the deseased, it doesn't matter because the world remains the same. It needs to be, because there are other people in need of those same quests. It makes no sense. And the solutions on hand (instancing, ghosting) make even less sense. The game world remains just a mess. The only way to do a story-based MMO is to follow the WWO route: limit all quest texts to 512 characters, and make reading them optional. The story in WOW, and in any MMO, is just like packaging a novel with your game (several game companies did this during the 90s): a nice touch, but it may as well not be there and the game would stay the same.
I agree, to some extent, about the PnP ruleset. It has been proven through many years of games around the globe and it has been adapted to computer games before. However, there are valid design reasons not to use it. For example, there is just too much variation in the results of single actions: the same attack can fail completely and do no damage at all, or result in a massive 3d12 critical. This is very hard to translate convincingly to an action game setting, where you expect to get predictable results to you button press. A game needs to stay very abstract and show you all the numbers if it is going to use a simulation system like that, and this is just not the direction games have been going for a long time.
You may be right, though, about doing a single player game first. This is the route Kingdoms of Amalur is going. But this means going through consoles first, and that is a very different beast.