Is this the Crosby AGA? (I assume you're not talking about the Olympia in the background of Photo 1.) I had an AGA back in the day and really liked it. I usually rode in a Crosby Prix des Nations, so I was used to riding in a saddle with no extra support. The AGA gave me a nice little knee roll for confidence over jumps. It also had a slightly wider regular tree than my PDN's which allowed it to fit more horses.
"I would get that piece of leather support behind the knee on the flap removed."
Do you mean there's a thigh/calf block under the flap that you'll remove? Or are you talking about the actual padding on the flap? My old AGA didn't have a thigh/calf block, and the very slight padding on the flap didn't affect my riding at all. I wouldn't recommend taking the padding out of the back of the flaps...it would probably be all saggy and would lower the resale value if you ever need/want to sell it.
I didn't even know they still produced the AGA! Just be sure you're getting one of the good Crosbys. Crosby was originally distributed by Miller's and were very, very high quality. Then they switched over to Walsall Riding Saddle Company and were still good quality out of England. For a brief time, the Crosby designs were sold off to Excelle which were by far inferior saddles. Now, I believe they're back to the Crosby name, but I'm not sure who produces them or what quality they are.