by my experience, the basic 4-way AV switchers you can get for $20 bucks at most places do just fine for older systems... they don't need anything complicated.
I highly, HIGHLY reccomend getting AV inputs for all the systems you can... the trick with using RF on a switcher is you'll need to plug it in for the RF to work- if you can even find a switcher with an RF input (I have one long discontinued box with 1 input that can do RF.) You can actually chain RF units together to hook up multiple systems that way, but obviously you'll get degraded signal the farther you go.