I haven't bought an Everdrive yet but when I do I'd love to do a system mod where the everdrive is mounted in the MD's case. I can easily de-solder the cart slot and extend it with wires similar to the Neptune mod (unless of course there's some where you can buy an extension cable), so it reaches the Everdrive wherever it's mounted in the case. I wouldn't really mind if the cart slot was no longer usable with actual cartridges however would there be a way to make it so the cart slot would override the Everdrive if I soldered an additional cart slot into the system? I just think a MD with a side mounted SD slot would be pretty cool. Pointless but cool all the same.
You could probably do it though you may need to add a switch to toggle between the cartridge slot and internal EverDrive/SD. I think it's a cool idea too. You could possibly mount some kind of switch that a cartridge would physically push sort of like the GBA had to sense when to enable GBC mode for knowing if you want to use the EverDrive or the Cart. I don't think there are any cartridge extension cables. Plus I don't think that would work to connect both the EverDrive and the Cart slot at the same time.
interesting idea MottZilla, especially if it was combined with a home-made neptune mod. You might loose 8-bit support due to the 32x as a down side. Also the chances of messing up the Everdrive would put me off.
If done right you could easily cut the Everdrive down to something quite small. Even more so if the PCB were redesigned.
I wouldn't bother with the 32X, I was just referring to the Neptune mod posted somewhere on these forums as it gave me the idea of desoldering the cart slot. I think I'll probably live without the cart slot too, a purely SD only MD would be pretty cool if I could come up with some kind of interesting case mod to blank/remove the cart slot.
You could always just put something under it and glue it shut or something so the dust flaps are always closed. Whatever you do, be sure to show off pictures of your mod when you complete it.