Actually, this would be a splendid idea to work into stock XCOM as an "advanced option" -- "Enable purchase of trained operatives".
It always bugged me how you were supposedly recruiting the best of the best from special forces around the world, yet they always panicked or couldn't hit the broad side of a barn.
Same issue with Mass Effect 1 --Shepard was supposedly a top grade special operative (the whole N7 thing on your suit), but shot like a rookie at the beginning of the game.
If you could buy decently trained operatives, it would I think help alleviate the 'save-scumming' so prevalent in X-COM -- because then losing someone wouldn't be a critical blow to your organization; since you could just buy a replacement "Falcon" (Chengdu Military Region Special Forces Unit) from the PRC.
Of course, you'd have to design it so that it wouldn't break the game horribly -- maybe work in a cool-down factor so you can't just purchase 30 top flight soldiers in a single month -- because I imagine the global pool of special forces operators capable of being "scrubbed" is pretty small!
[By scrubbed, I mean all traces of their existence were wiped from all global government databases. Why? Just imagine the stink if a former US Delta Force operative was found dead in mainland China with a 10cm plasma hole in his chest, or vice versa!]