Long ago, when I had free time, nearly unlimited G1 parts, and lots of paint, I created a double decker City transformer, in the image of Optimus. 

 

Made a 2 garage, 2 hellipad Metroplex, by bashing together 1 and 1/2 of him.  Slapped in the head master port, and topped it off with a Hero Optimus missile launcher, and tripple changer micromaster Optimus/truck/head. 

 

I like the convept...however its not the greatest looking thing I ever made.  I am most proud of the Headmaster tripple action out of anything else. 

 

Used some mold making tricks to make a cast of a PM prime super mode face, and made a new out out of hotglue, and grafted it to the MM's back.  Then stuck in some plastic tabs to work the Headmaster meter, the toy's head worked like a HM head peg on its own and was perfect for the job.  I drilled 2 large holes in his sides for the Metroplex Antlers to fit in. 

 

Young friend of mine named Jeff B, came up with a similar idea for a Optimus Base, and created one that I think looks a lot better in robot mode, but doesn't have the features I tried to cram into mine.  In the botcon shots, his is on the right.  He called his Orion. 

I think yours looks good however I might suggest getting a 0/3 brush and slim the eyes down some. The eyes are a little too large.

Its in a box, i pieces now.  So repaint Ain't gonna happen. 

 

If I do put i back together some day, I might make it look more like this...

 

I think it looks like Max this way. 

What I think would look really sweet would be to hook the five G1 Aerialbots to him like G1 Metroplex did.