Which Radio?

I have 4 trucks. All of which have brushless systems in them. I am wanting to upgrade to a better radio system. Maybe something sysnthesized. I want to be able to run it on all my trucks. But I still want to be able to use other transmitters with the other trucks in case I have friends over. What is the best way to do this.

1. Rustler- GTB 5.5 (This I run the most0

2. Rustler- SS5800 (Run it sometimes-usually there for friends to drive or family0

3. Emaxx- HV-Maxx(Here and there, not to often.)

4. Stampede- 8s/MGM80(Work in progress)

These are my trucks , what is the best way to get FM in them but have the ability to run them separately. My main focus is to be able to get one radio in my hand for all cars while still having backup radios when I have company. Does this make since? Thanks in advance.