Well that wouldn't make it any more realistic because then you wouldn't have to press start. The poster is talking about adding real coin input and having the games detect coins, show an insert coin message, ect....
Long story short with the exception of the dreamcast games above this isn't gonna happen. As the others have said, this would require altering the internal code of the game rom, which I don't think anyone is willing to do just for a puny insert coin message.
In order for a front-end to do it it would have to grab frames and super empose an insert coin message at 30+ fps full screen. This is hard enough, but then it would have to be rigged to figure out when your game is over, when it's time to continue, ect... So really I see no way this could be done without some interaction with the rom, and as I said, ain't gonna happen.