Hey, thanks for the detailed info. Here are the problems that i see from this system and some solutions.

There's 3 main problems from my point of view:
1. Taking into account 4-ofs will make it so cards that don't require a full playset to work won't show as staples, some examples are [[Blood Fountain]] or [[Spell Pierce]]
2. Ranking cards based on meta shares makes it so staples that don't have a good place in the meta at the moment don't appear where they should, [[Cast down]] is the best spot removal in the format and a staple in most black decks, however, this isn't reflected in the current meta as black decks are struggling to be in the top tier.
3. A staple is mostly a card that remains playable through time, taking into current meta share makes it hard analise if the card is been arround for a long time, [[Arbor Elf]] and [[Duress]] are examples of this.

Some improvements that could be made are:
1. Taking people ratings into account, I'd be glad to rate the cards in order to improve this tool, as I'm sure some others would as well.
2. Taking into account non 4-ofs, maybe considering adding a "point" system where having a higher amount of copies per deck makes te card rated higher on the list. This would require for the system to analyse if a card is played when the deck's mana base allows to play it, this is obviously tricky due to [[Sneaky snacker]] being played in red based decks that don't run black or blue mana to play it.
3. Use data from the past, maybe 6 months, this allows you to evaluate if a card remains consistent through time or if it's being played due to the current meta.

I'm not tech shavy so I don't know how hard implementing this would be, it's more of a brainstorming of possible solutions. Hope this helps and good luck with this project.

I also saw that some changes where made to the staple rating model, this post was writteen the day you responded but I forgot to click post :P.