A catalog (or similar ordering system) that you could buy from Pierre's (or Joja, if you go that route) that offers a limited quantity of next season's seeds to be delivered on the first day of the season so you can get planting before the store opens that season? Edit: Possibly also some kind of "limited edition" furniture/deco items not sold in Pierre's/Joja?
OTOH part of the game is the stepped progression. If you saved some fruit or veggies and have a seed maker you can do that on your own, so although it would simply things I think it would be an endgame implementation and so to most players, superfluous.
I have to agree with Fuzzyman, the way seeds are made available is part of the progression and, more importantly, flow of the game. It encourages making the decision to stockpile some produce for use in seed makers once you have them, and finding that sweet spot of how much product profit to sacrifice for the sake of availability next year.
