There's enough space left for a built-in cartridges rack.
Yea, unfortunately there is still a lot of other things that need to fit in there. the CGA to VGA Board, the audio amplifier, case fans, terminal strips, and a crapload of wires...
The cartridges rack should be installed on the top part of the space, with carts facing out the back of the cabinet. All the other things you mentioned could be installed in the base, on the right and back of the Neo-Geo motherboard.
If nothing has changed, your marquee should be more or less 15.35 x 3.56~5.00 inches. According to EMDKAY, Neo-Geo mini-marquees are <a href="
http://emdkay.net/catalog/pulstar-mini-marquee-p-239.html"> 4.5 x 5.5 inches</a>, meaning you can't use them on your cabinet. Of course, you could order scaled-down mini-marquees (I'm sure EMDKAY and others can make smaller mini-marquees).
You could also add a barcode scanner and put a barcode label on your carts (on the left or right), wire up a microcontroller and you'd be able to have an automatic mini-marquee LCD that updates itself according to the cart in the motherboard.
Again, according to EMDKAY, the <a href="
http://emdkay.net/catalog/slot-marquee-p-116.html">single-slot Neo-Geo marquee is 26 x 8 inches</a>.
Some quick calculations:
- original marquee = 26 x 8 inches, with 4.5 x 5.5 inches mini-marquees
- your marquee = 15.35 x ~3.56-5.00, with 2.65 x 3.25 inches mini-marquees, requiring an LCD display around 4.2 inches diagonal.
In any case, I don't remember where I got it, but attached is a high-resolution single-slot (space for one mini-marquee) Neo-Geo marquee graphic. It's a PNG file so there's no artifact and it's gonna be easy to modify if you need to move things around a bit or redraw the mini-marquee rectangle and cutout.