slot expansion are by the way not expansion themselves but just a way to enable allow more expansion ... 
what are you saying...? XD
if you have concerns about limited slots on you rmachine try to think to gather interfaces on the same board like this one : sd+ethernet+usb
it does not require special skills , it is easy , you can do it 
Make a single board with different interfaces is easy (in the same way that i said), hook slot expander logic on board then you have X-0 X-1 X-2 X-3 then you can add SD,flahrom SCC and what you need.
And yes, I did it 
http://www.flickr.com/photos/44218601@N06/4061380894/sizes/l/in/set-72157622577967051/
You can see "fmpac" cartidge(real fmpac board is behind of it): it has dual SD with megaflashrom SCC (switch control), and X-0 and X-2 free slot select signal for adding more interfaces :P
having scc+ 2sd on the same board & slot is good : it gathers 2 functions.
Why not , the same way, gathering more functions ? like the example i gave ?
In this device you save space & connector & need for slot expander.
So you can understand it is very different from putting expansion with
a slot exander, you dont even have to open your msx case,
but dont get me wrong : your flickr galleries look very nice!
Hey! Still looking. I also have a good condition C64C to trade - as well as cash. I saw this and it was GORGEOUS!
