Something like Dr_Newbie's mod, but with binds for hands and weapon. If you press X key, hands become invisible, press it again, visibile; same with the weapon. Save feature so the config isn't lost in between heists.

This other one is something I thought about while playing Quake. Quake Live have this feature where you could use a slider (or command - r_drawviewmodel) to make your weapon more or less transparent: 0 to 1 slider (0.4 would make your viewmodel 40% transparent, for example). Save feature so the config isn't lost in between heists.