I don't know about specific load times, but I believe Darksoft was planning to have a four slot system where you can load four games into memory and have them available to pick from. Similar to the idea of a four slot MVS cab. Just toggle between the four games.
What about mapping the four slots to the four controller buttons?
As you scroll through the games you could press A to load games into slot 1, B for slot 2, etc. If a game already exists in that slot you have a popup confirming the overwrite.
Select button to erase/empty a slot, using the...
I like the bottom half with the numbered slots, that is clean and straight forward for use.
As for picking games I would be perfectly fine with a A-F, G-L, M-R, and S-Z sub menu, then you would have less to scroll through at any given time.
But to be perfectly fair, I am used to scrolling...