Fake players are not necessarily a bad thing. You don't have to program them to fix the game as the company pling worked for did. You can make them perform as average players or even weak ones (so you have many winning and happy real players). You decided to openly advertise them as NPCs and that's ok but you might have just hinted about their nature. Plenty of games have bots and NPCs. Actually, up to the time of Internet games everybody played against bots all the time and the end level bosses were usually very strong. Nobody complained (too much) about it.