Suggestion for the store

Even though many would oppose to the idea of having the store expanded, I’m as a mostly F2P player (only paid in roughly €40,- total) getting trouble upgrading my mini’s for lack of uograde cores.
Wouldn’t it be an interesting idea to have upgrade cores as part of the store, to purchase them for gold? As gold is collected throughout playing the game, it could still be considered “free”.
This, instead of the random daily options.

At this moment, i have atleast 4 or 5 mini’s waiting to be upgraded to rare, but cant due to lack of cores. What I can get relatively faster, is the gold to buy them if I would also have the option to.

Thanks for considering.

Kind regards,
Trux