The only Autobot base I had was that cardboard one that came out in the 80's.
I have never had Metroplex, Fort Max, or Omega Supreme.

Is there a way to combine all four of these base elements to work together? It might be cool to see some ways of putting them together if someone wants to post some pics  

 

I've got a modded Brave Max, Scorponok and Metroplex and other than trying to connect a bridge here and there, there really isn't much you can do...

There were three guys in the Japanese series that could combine into one big base... One was Dai Atlas... Can't remember what the other two were...

 

Roadfire and Sonic Bomber I think. They combined into Big Powered in alt modes, I can't remember if they combined in base modes. It might just be a matter of attaching ramps between them like with the other micromaster bases.

If you want to see some huge TF city building, get the micromaster bases. I can think of at least 13 figures off the top of my head than can all attach via ramps, and that's not counting the big bots like Dia Atlas and co or Star Convoy and co.

 

I got Dai Atlas and it makes for a very nice base mode, actually better than Metroplex in my opinion.