You're correct in that we won't see a new Mark 1 after this current one for quite some time. That's why it ultimately comes down to whether or not you care more about just having the figure in your collection or if it's shortcomings are too much for you to look past.
For me, the Mark 1 figure is just way too off the mark for me to even consider paying for. I rather not have a Mark 1 in my collection than have one that's tiny and off looking when on display. It's probably fine if you just display it on it's own but for most people that's not how their display setup is.
Not paying $455+tax+shipping for that one. I'm also happy with not having every single Mark suit out there. I narrowed it down to key movies or events. Stick with the Mark 7 and this BD Mark 85 to represent the first Avengers and the last. Couple that with the 2012 Captain America and the End Game Cap to display together.