I debug by removing the top cover of my TM503 or the left, right, and top sides of my TM5003.
That gives almost as good access as the pictured "naked" TM502.
But my problem with an FG507 plug-in is with the power supply.
I'd like to use my bench supplies to send the +/-33V and debug it from here.
The connector would allow me to do that without having to solder wires on leads of components on PCB.
Regarding the extenders, my goal is not to sell kits.
But rather to design an edge PCB car, put the Kicad sources and gerber files.
So anybody can have one fabricated and buy the needed parts.
By the way, John, your Taiwan source, how much does a connector cost?
The EDAC ones are almost 17 euros!