I have done the "lusting after" bit. I get some strange thing fixed in my mind as a "must have." It has never been a coupler.
I have never missed. The first one was an MM-2 in 17/64. I lusted for that beast from about 1957 to 1984, knowing that I would have to build it. I now have four.
Then it was the Lobaugh Cab Forward. I placed a bunch of ads in MRR and 48/ft, and one day Peter Thorp (RIP) agreed to sell me his.
My current project in that vein is a sand- cast Erie-Built. The sides (the last pieces I need) are now at a foundry. It has been maybe 20 years in its inception.
I think this sort of thing, if kept under control and in perspective, can be entertaining and healthy. If it becomes an obsession it can be harmful.
Opinion.