That presents a bit of a problem with environmental damage. A lot of dust can settle in the unoccupied spaces, causing some the base to deteriorate.

I may be explaining it wrong so I drew a picture.

so the base would also be inside the frame.

I was actually thinking about the same sort of thing. Except there wouldn’t be walls on the side. Having walls would stop you having buttons, USB, headphone jacks etc.

You bring up a good point about the buttons. Maybe have a slot on the sides where you slide the block in sideways? Like a DVD or memory card on a laptop. Just have a thicker slot. Most phones have the ports at the top or the bottom of the phone so I think it would be feasible if the ports were at the top or bottom. You could have the standard ports already in the frame.

Or another idea you could have slots on all four sides of the device. Have the main block (OS and processor) in the middle. This one would push straight down like the original idea. Then have the components slide in from the side. This may even make the design process (on the electronic side of the coin) easier because all parts would connect to the OS in the same manner.

Each slot could have (I’m just throwing numbers out here) 20 connections. Depending on the component only one or two connectors will be used. Then the corresponding pin would match up where it needs to on the processor side. The block manufactures would need to follow a pin standard. But there would need to be some sort of standard for this to work anyway.

I would prefer an extra case that have rounded egdes and protect the phone from water and falls the same time