Doing a quick search on the newegg website, saw there a 14.5" notebook with a reasonably good enough GPU for some games.
The CPU is a Core i5 460M, dual-core 2.53GHz, it has 4GB DDR3 RAM, and the GPU is a Mobility Radeon HD5650, which is comparable to the desktop Radeon HD5570, but with lower clocks.
Based on the specs, this notebook should be able to play some games that have low requirements with high settings (like the Call of Duty series), others with medium settings (for example Crysis should be playable at medium settings with a framerate around 20~30fps), and even some games with heavier requirements might be playable with lower settings.
Now about PSO2, since nothing is known about it, no one knows if it'll be playable in a notebook like this or not. If PSO2 is anything like the mess that is Final Fantasy XIV, it might be unplayable (or nearly unplayable) in this notebook. But if PSO2 is being done first with the PC in mind, I think it's possible that it won't have too high requirements like FFXIV.