It surprising how noobs can trust everything .....
Well you know TheAstronomo, making a mod isn't a thing easy, and in my opinion developers have enough work to do on BTTF HV for Vice City, and they have a life. So first, let them finish BTTF HV (something like 2 or 4 years) and then, ask them. If you don't want to wait, learn programmation languages and make your mod yourself.
Oh and Grim is right : You can run in Episode from Liberty City, but you CAN'T run BTTF HV in Episode for Liberty City. Makes sense, doesn't it ? ( Same thing for GTA IV)