They have always connected the two which lead to players having to decide whether they want to roleplay or win the game; an interesting, but completely unfun decision.- Nils commenting at Procrastination Amplification
Why is winning separate from roleplay? Or if you don't like that term, try choice of play or style of play. It doesn't make much sense. Would a Light character win the same way as a Dark character? Of course not. But beyond that, they'd define winning differently. For Palpatine it was dominance over the galaxy while for Luke it was freedom and protecting his friends.
Perhaps win isn't even the right word. Success. Goal completion. Different people have different goals. President Obama and Speaker Boener have a conflicting goal regarding the 2012 election. They have a shared goal in economic recovery, but their methods will be very different. So even for the same goal, the same winning condition, we see significantly different methods.
The win condition should not be a single absolute in a game with morality or other types of choice, but should instead be based on how the player plays. This could be done in a sandbox way, by allowing greedy players to get rich and murderous players to kill while altruistic players protect everyone. But sometimes people like their credit roll or victory screen. At the least it confirms that they've done what they thought they had, which in the specific case of "kill everyone" can be difficult to determine if the victims move around a lot.
Let's try the example of the Civilization series. There are definite winning conditions, all of which give a win (duh), but in different ways. The key part is that you win by playing well in the way you choose to play. Science victories come from technological progress while cultural victories come from cultural gain. You wouldn't get a conquest victory from either method, but instead from a different way: killing everyone.
Applying this to a gear-centric, or even just gear-using, MMO is not as easy. If you're +3 Light and your decisions tend to keep you there and there is a nice +4 Light cloak, the game would have to somehow not cause you to want the +4 Light cloak. Otherwise there is incentive to play away from the character's personality in return for reward, which is often not much fun.
The different Shades (Light-Dark) of gear could boost stats or behaviors related to actions which cause that Shade. For example, maybe a player does a little too much theft to be +4 Light, so the +3 Light cloak helps with theft, but less than a +2, and much less than a -4 Dark. But this carries many problems. For one, there are multiple reasons for a Shade and not all of them are stats to be boosted. Maybe a player has a murder but no theft, so the +3 Light cloak with added theft is useless.
Light-Dark power costs could be one source, with a Light Side and a Dark Side energy pool, each supplemented by gear. A +4 Light player would have little to gain from a +3 cloak that mixes mostly Light with a little Dark, while the +3 Light player would not want to lose the bit of Dark energy, and the flexibility, from going to a +4 Light cloak. Unfortunately this solution lends itself heavily toward gear/stat-obsession, but even worse, is really damn boring.
P.S. Yes, this is tagged Star Wars Galaxies. That's the tag I have and I'm sticking with it, search engines be damned.