This idea which i think will remove the tedium of the seed vaults is to have the seed menu when managing your plants to include all the seeds in your vault, i would say this should be on a sub menu of the seed menu, have that will allow for you to only look at your backpack seeds or your vault seeds separately.
another Idea is having housing items effect plants, slimier to how plants don't like other plants, this would make it so you could have an orchered of snow/ whatever type of apple trees mixed in with decorations and it would improve the quality of the output of those apple trees.
things like fly traps would have the same happen when being near swamp like things, this allows for people to have creative and while still getting benefits.
im unsure what the red barn does for plants but if it does just make plants give a better output then this idea is similer to that, only it will be a build up, as to incentivize putting more work into combining plants and decorations, the benifit should only go up to how much the red barn gives.
also new plant type/new plant effect, i know that we have spells to get rid of pests but that shouldn't be the only way to do it, i prepose we get a new plant type, fly swatters or fly whips or some clever pun about them.
these would effect other plants in the area near them, as they swat away bugs, there would be versions of these that effect higher ranked pests, this effect would also be given to fly traps though it would be up to kings isle how much of an effect they would be, perhaps a chance to eat clear itself of pests?
anyway this would let you garden effectively seeing how IRL you can use other plants to ward off pest type bugs