You can always get an RGB (23pin) to SCART cable from AmigaKit just to have it as spare for times of desperate measures or even for having it to connecting easily your A4000 to your LCD/TV, TV etc. 
Yes, my problem would be what LCD/TV would work, but it might help.
There is another thing, in your excellent demonstration of how to use the
add hard drive feature in UAE you mention that it is easy to see what drive you want because of the RDB descriptor. I don't see RDB, but in the same place I have MBR. Is this relevant?
I can make the thing run but it shows a request to insert a floppy disk into a floppy drive.