While you are playing with psapi you can look at ReactOS's psapi.dll and see if it implements something that WINEs psapi doesnt. We relicensed it under LGPL about a month ago so if there is anything there that can help WINE feel free to rip it.
ReactOS implementation (at least the last time I looked at it), was heavily relying on process implementation in memory, which I'm not sure matches exactly with wine's reuse might not be that easy A+