So, after building countless PC's and many custom rigs in pre-made cases I've decided to challenge myself in the new year by building an entire custom case from scratch. I already have an idea of what I want to build but I have some questions about motherboard and GPU mounting orientation and I'm hoping you all can help.
 
I'm planning on creating a scale model of the W.O.P.R. computer from WarGames. My whole home office is done in a Fallout inspired theme and I feel like this will fit in perfectly. Here's a poor reference picture.
 


 
My plan right now is to use the longer, shorter side to house the motherboard and the taller side to route the external cables and hold the solid state drive. This means I need to put the motherboard ports on the right side of the case. This presents me with a problem as  there's only two ways to really do that as far as I can tell.
 
One is to mount the motherboard to the front interior of the case in a normal orientation. This causes a problem as I want my radiators to be on the rear of the case and would make working on it very difficult. 
 
The other is to mount the motherboard upside down. This would allow me to have the ports on the right side of the case and run the cooling hoses under the bottom of the motherboard tray. When I remove the case top it would be just like working in a normal tower. 
 
Is there anything wrong with mounting the motherboard and GPU upside down?