I am going to play the Pokemon TCG again and I plan to purchase my deck in the highest rarity (SIR/IRs) of the Pokemon only and supporters.
As the game rotates out of standard, instead of selling the cards; I am planning on putting at least 1 of each quantity card into a binder and it’'d be kinda like a history of the Pokemon/Supporters I played with.
Sure! I mean, the idea of keeping your favorites separate is always a good idea, especially for the memories. A number of my decks (constructed and draft) remain alive even decades later simply because I don’t want to lose track of the very cards that I won tournaments with. 
If you like it, it’s a cool idea. Forget everyone else.
But yes, that does seem like a cool way to collect the cards you spent time playing with.
Will you buy Max priority for cards that you’re just testing out? Typically I try and keep them at reverse foils or non-foils. I’ll play with it and rotate cards out as needed, once the deck moves on I keep it. I don’t have any decks dismantled and I tend to build other notable decks that I played against that way I can maybe one day relive it.
Yeah I plan on maxing everything I test out regardless if I don’t use em anymore
That’s kinda how I started my FA collection. Brigette, Guzma, M Alakazam - each was in my original deck. 
I think cataloging your decks to remember the fun times is a great idea!
