I think that, if Cordy had still been alive in Season 5, she would have been the one member of the gang who would have been in on the bargain from the very first, or would have figured out from the beginning that W&H had something important hanging over Angel's head, and kept pestering him until, by no later than the 2nd commercial break of the 3nd show, would have found out exactly what was really going on. She just knew him too well by that time NOT to have been in on the deal very quickly.
As for what her job would have been, I couldn't see her being anything other than Angel's REAL Executive Assistant, with Harmony as the secretary/receptionist whose main job was to be sure that Angel got his warm otter blood promptly. (Come to think of it, that's just about what Harm actually was anyhow) In the final showdown, she would have been the one who got word to Connor that the s**t was about to hit the fan, and he'd better come a'running. Then she and Harm would have had a little girl to girl chat about the good old days in Sunnydale High, sharp pointed instruments, and how maybe a semi-reformed vampire might have a much better chance of making a go of things somewhere like the former Soviet Union.
She would have also gotten word to Buffy (probably just slipped her a note sometime during one of the Slayer's frequent trips to visit Spike) that Angel was about to screw up yet AGAIN, and that a small army of assorted demon fighters would have been a handy thing to have on sight.
