Tree grafting.

[Granger]

Apart from decay not functioning on unloaded maps (thus repopulation of tree products falling short unless you idle an alt in the area) my issues with tree is:
Most of them are useless (apart from decorative reasons), one would raise only one bough type for picks/saws/bows while everything else is purely fruit types (or byproduct of the silk farm) as these can be cycled way quicker (early seeds) and reliable (more seeds so stunting is no issue).

Having to jump through additional hoops that slow down fruit tree quality increase would be welcome, grafting could present the opportunity to give more trees a purpose: like type x branch only working on y type stem, or (more lenient) each fruit having a preferred stem type while on others the speedup till they bear fruit is way less (though faster than planting from the fruit seed directly).

End result should still be slower raise in quality compared to now, preferably removing spirals to open the way toward an eternal world.