In my suggestions above ^ the person with the hoard has not been in any way punished beyond the crappy F grade. I only suggested perks for those OCD collectors that want a completion of 100%. I don’t think this should be done for variants, only cards that count towards the 100%. If you are a hoarder and you do not trade them away, that’s your prerogative, but there should be other options opened up for people that want 100% - like the limited filtered print release, or placeholder idea.
For people that do not participate and never trade? - different subject entirely, but since someone brought it up -> I think there should be a different tier for them. It’s like PvE or PvP - usually on different servers. Or raiders vs casual - usually different guilds and access to different gear/rewards. I think that if you are an F player, and stay F, you should be limited in something… maybe the number of free packs each day goes down after three weeks or some such. I have no idea what, but they definitely shouldn’t be on my trade list to wade through.
People with A+, or who accept incoming trades, or counter them regularly. People who actively push the decline button, and not letting things expire? There could be “streak” counts. “You’ve accepted 10 incoming trades in a row! Amazing job! Here is a pack” – wow that is awesome, why thank you yes I have been accepting all trades haven’t I? Or “Hey you have offered 3 trades in a row, good job! Want to brag?” or “Congratulations, you have made 5 trades today, here’s a credit”
Or, my favourite suggestion: “Hey you’ve been grade A+ for over a month. Good job! You have been granted access to the GOLD artwork of this one pack that is only opened for people with A+ for over a month” or “You have been C+ for over a week, good job! Here is access to a few new artists because you have maintained a good standing”.
You know who else offers streaks and perks and rewards? Every game. Every job. Every school.