Grand Theft Auto 4 mod allows you to switch characters ala GTA 5

Rockstar's upcoming Grand Theft Auto 5 will shake the studio's best-selling open-world template up a great deal by introducing the option to switch between three characters on the fly while the two unpossessed members will continue going about their business. Now, some clever modders have created a way to implement this into Grand Theft Auto 4.With the mod installed, you'll be able to hop between roles as GTA 4 protagonist Niko Bellic, The Lost and Damned's Johnny Klebitz, and The Ballad of Gay Tony's Luis Fernando Lopez. Whoever you're not playing as will wander the streets on their own or attempt to evade the cops if they have a wanted level greater than zero. Each character has their own health, armour, ammo and vehicle which are saved every time you swap roles.

http://www.eurogamer.net/articles/20...ters-ala-gta-5